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World War I
|World War I|
Clockwise from the top:
| Allied Powers:
|Commanders and leaders|
|Total: 42,950,000||Total: 25,248,000|
|68,208,000 (Total all)|
|Casualties and losses|
Military deaths by country:
Military deaths by country:
World War I (or the First World War, often abbreviated as WWI or WW1; German: Erster Weltkrieg) was a global war originating in Europe that lasted from 28 July 1914 to 11 November 1918. Contemporaneously known as the Great War or "the war to end all wars", it led to the mobilisation of more than 70 million military personnel, including 60 million Europeans, making it one of the largest wars in history. It is also one of the deadliest conflicts in history, with an estimated 9 million combatant deaths and 13 million civilian deaths as a direct result of the war, while resulting genocides and the related 1918 Spanish flu pandemic caused another 17–100 million deaths worldwide, including an estimated 2.64 million Spanish flu deaths in Europe and as many as 675,000 Spanish flu deaths in the United States.
On 28 June 1914, Gavrilo Princip, a Bosnian Serb Yugoslav nationalist and member of the Serbian Black Hand military society, assassinated the Austro-Hungarian heir Archduke Franz Ferdinand in Sarajevo, leading to the July Crisis. In response, Austria-Hungary issued an ultimatum to Serbia on 23 July. Serbia's reply failed to satisfy the Austrians, and the two moved to a war footing. A network of interlocking alliances enlarged the crisis from a bilateral issue in the Balkans to one involving most of Europe. By July 1914, the great powers of Europe were divided into two coalitions: the Triple Entente, consisting of France, Russia, and Britain; and the Triple Alliance of Germany, Austria-Hungary, and Italy. The Triple Alliance was only defensive in nature, allowing Italy to stay out of the war until April 1915, when it joined the Allied Powers after its relations with Austria-Hungary deteriorated. Russia felt it necessary to back Serbia, and approved partial mobilisation after Austria-Hungary shelled the Serbian capital of Belgrade, which was a few miles from the border, on 28 July. Full Russian mobilisation was announced on the evening of 30 July; the following day, Austria-Hungary and Germany did the same, while Germany demanded Russia demobilise within twelve hours. When Russia failed to comply, Germany declared war on Russia on 1 August in support of Austria-Hungary, the latter following suit on 6 August; France ordered full mobilisation in support of Russia on 2 August.
Germany's strategy for a war on two fronts against France and Russia was to rapidly concentrate the bulk of its army in the West to defeat France within 6 weeks, then shift forces to the East before Russia could fully mobilise; this was later known as the Schlieffen Plan. On 2 August, Germany demanded free passage through Belgium, an essential element in achieving a quick victory over France. When this was refused, German forces invaded Belgium on 3 August and declared war on France the same day; the Belgian government invoked the 1839 Treaty of London and, in compliance with its obligations under this treaty, Britain declared war on Germany on 4 August. On 12 August, Britain and France also declared war on Austria-Hungary; on 23 August, Japan sided with Britain, seizing German possessions in China and the Pacific. In November 1914, the Ottoman Empire entered the war on the side of Austria-Hungary and Germany, opening fronts in the Caucasus, Mesopotamia, and the Sinai Peninsula. The war was fought in (and drew upon) each power's colonial empire also, spreading the conflict to Africa and across the globe. The Entente and its allies eventually became known as the Allied Powers, while the grouping of Austria-Hungary, Germany and their allies became known as the Central Powers.
The German advance into France was halted at the Battle of the Marne and by the end of 1914, the Western Front settled into a war of attrition, marked by a long series of trench lines that changed little until 1917 (the Eastern Front, by contrast, was marked by much greater exchanges of territory). In 1915, Italy joined the Allied Powers and opened a front in the Alps. Bulgaria joined the Central Powers in 1915 and Greece joined the Allies in 1917, expanding the war in the Balkans. The United States initially remained neutral, though even while neutral it became an important supplier of war materiel to the Allies. Eventually, after the sinking of American merchant ships by German submarines, the declaration by Germany that its navy would resume unrestricted attacks on neutral shipping, and the revelation that Germany was trying to incite Mexico to initiate war against the United States, the U.S. declared war on Germany on 6 April 1917. Trained American forces did not begin arriving at the front in large numbers until mid-1918, but the American Expeditionary Force ultimately reached some two million troops.
Though Serbia was defeated in 1915, and Romania joined the Allied Powers in 1916 only to be defeated in 1917, none of the great powers were knocked out of the war until 1918. The 1917 February Revolution in Russia replaced the Monarchy with the Provisional Government, but continuing discontent with the cost of the war led to the October Revolution, the creation of the Soviet Socialist Republic, and the signing of the Treaty of Brest-Litovsk by the new government in March 1918, ending Russia's involvement in the war. Germany now controlled much of eastern Europe and transferred large numbers of combat troops to the Western Front. Using new tactics, the German March 1918 Offensive was initially successful. The Allies fell back and held. The last of the German reserves were exhausted as 10,000 fresh American troops arrived every day. The Allies drove the Germans back in their Hundred Days Offensive, a continual series of attacks to which the Germans had no reply. One by one the Central Powers quit: first Bulgaria (September 29), then the Ottoman Empire (October 31) and the Austro-Hungarian empire (November 3). With its allies defeated, revolution at home, and the military no longer willing to fight, Kaiser Wilhelm abdicated on 9 November and Germany signed an armistice on 11 November 1918, ending the war.
World War I was a significant turning point in the political, cultural, economic, and social climate of the world. The war and its immediate aftermath sparked numerous revolutions and uprisings. The Big Four (Britain, France, the United States, and Italy) imposed their terms on the defeated powers in a series of treaties agreed at the 1919 Paris Peace Conference, the most well known being the German peace treaty: the Treaty of Versailles. Ultimately, as a result of the war, the Austro-Hungarian, German, Ottoman, and Russian Empires ceased to exist, and numerous new states were created from their remains. However, despite the conclusive Allied victory (and the creation of the League of Nations during the Peace Conference, intended to prevent future wars), a second world war followed just over twenty years later.
The term "world war" was first used in September 1914 by German biologist and philosopher Ernst Haeckel, who claimed that "there is no doubt that the course and character of the feared 'European War' ... will become the first world war in the full sense of the word," citing a wire service report in The Indianapolis Star on 20 September 1914.
Prior to World War II, the events of 1914–1918 were generally known as the Great War or simply the World War. In October 1914, the Canadian magazine Maclean's wrote, "Some wars name themselves. This is the Great War." Contemporary Europeans also referred to it as "the war to end war" or "the war to end all wars" due to their perception of its then-unparalleled scale and devastation. After World War II began in 1939, the terms became more standard, with British Empire historians, including Canadians, favouring "The First World War" and Americans "World War I".
Political and military alliances
For much of the 19th century, the major European powers had tried to maintain a tenuous balance of power among themselves, resulting in a complex network of political and Military alliances. The biggest challenges to this were Britain's withdrawal into so-called splendid isolation, the decline of the Ottoman Empire and the post-1848 rise of Prussia under Otto von Bismarck. Victory in the 1866 Austro-Prussian War established Prussian hegemony in Germany, while victory over France in the 1870–1871 Franco-Prussian War unified the German states into a German Reich under Prussian leadership. French desire for revenge over the defeat of 1871, known as revanchism, and the recovery of Alsace-Lorraine became a principal object of French policy for the next forty years (see French–German enmity).
In 1873, to isolate France and avoid a war on two fronts, Bismarck negotiated the League of the Three Emperors (German: Dreikaiserbund) between Austria-Hungary, Russia and Germany. Concerned by Russia's victory in the 1877–1878 Russo-Turkish War and its influence in the Balkans, the League was dissolved in 1878, with Germany and Austria-Hungary subsequently forming the 1879 Dual Alliance; this became the Triple Alliance when Italy joined in 1882.
The practical details of these alliances were limited, since their primary purpose was to ensure cooperation between the three Imperial Powers, and to isolate France. Attempts by Britain in 1880 to resolve colonial tensions with Russia and diplomatic moves by France led to Bismarck reforming the League in 1881. When the League finally lapsed in 1887, it was replaced by the Reinsurance Treaty, a secret agreement between Germany and Russia to remain neutral if either were attacked by France or Austria-Hungary.
In 1890, the new German Emperor, Kaiser Wilhelm II, forced Bismarck to retire and was persuaded not to renew the Reinsurance Treaty by the new Chancellor, Leo von Caprivi. This allowed France to counteract the Triple Alliance with the Franco-Russian Alliance of 1894 and the 1904 Entente Cordiale with Britain, while in 1907 Britain and Russia signed the Anglo-Russian Convention. The agreements did not constitute formal alliances, but by settling long-standing colonial disputes, they made British entry into any future conflict involving France or Russia a possibility. These interlocking bilateral agreements became known as the Triple Entente. British backing of France against Germany during the Second Moroccan Crisis in 1911 reinforced the Entente between the two countries (and with Russia as well) and increased Anglo-German estrangement, deepening the divisions that would erupt in 1914.
The creation of the German Reich following victory in the 1871 Franco-Prussian War led to a massive increase in Germany's economic and industrial strength. Admiral Alfred von Tirpitz and Wilhelm II, who became Emperor in 1890, sought to use this to create a Kaiserliche Marine or Imperial German Navy to compete with Britain's Royal Navy for world naval supremacy. In doing so, he was influenced by US naval strategist Alfred Mahan, who argued possession of a blue-water navy was vital for global power projection; Tirpitz translated his books into German, and Wilhelm made them required reading. However, it was also driven by Wilhelm's admiration of the Royal Navy and desire to outdo it.
This resulted in the Anglo-German naval arms race. Yet the launch of HMS Dreadnought in 1906 gave the Royal Navy a technological advantage over its German rival, which they never lost. Ultimately, the race diverted huge resources to creating a German navy large enough to antagonise Britain, but not defeat it. In 1911, Chancellor Theobald von Bethmann-Hollweg acknowledged defeat, leading to the Rüstungswende or ‘armaments turning point', when Germany switched expenditure from the navy to the army.
This was driven by Russia's recovery from the 1905 Revolution, specifically increased investment post-1908 in railways and infrastructure in its western border regions. Germany and Austria-Hungary relied on faster mobilisation to compensate for fewer numbers; it was concern at the closing of this gap that led to the end of the naval race, rather than a reduction in tension elsewhere. When Germany expanded its standing army by 170,000 men in 1913, France extended compulsory military service from two to three years; similar measures taken by the Balkan powers and Italy, which led to increased expenditure by the Ottomans and Austria-Hungary. Absolute figures are hard to calculate, due to differences in categorising expenditure, while they often omit civilian infrastructure projects with a military use, such as railways. However, from 1908 to 1913, defence spending by the six major European powers increased by over 50% in real terms.
Conflicts in the Balkans
In October 1908, Austria-Hungary precipitated the Bosnian crisis of 1908–1909 by officially annexing the former Ottoman territory of Bosnia and Herzegovina, which it had occupied since 1878. This angered the Kingdom of Serbia and its patron, the Pan-Slavic and Orthodox Russian Empire. The Balkans came to be known as the "powder keg of Europe". The Italo-Turkish War in the 1911–1912 was a significant precursor of the World War I as it sparked nationalism in the Balkan states and paved the way for the Balkan Wars.
In 1912 and 1913, the First Balkan War was fought between the Balkan League and the fracturing Ottoman Empire. The resulting Treaty of London further shrank the Ottoman Empire, creating an independent Albanian state while enlarging the territorial holdings of Bulgaria, Serbia, Montenegro, and Greece. When Bulgaria attacked Serbia and Greece on 16 June 1913, it sparked the 33-day Second Balkan War, by the end of which it lost most of Macedonia to Serbia and Greece, and Southern Dobruja to Romania, further destabilising the region. The Great Powers were able to keep these Balkan conflicts contained, but the next one would spread throughout Europe and beyond.
On 28 June 1914, Archduke Franz Ferdinand, heir presumptive to the Austro-Hungarian Empire, visited the Bosnian capital, Sarajevo. A group of six assassins (Cvjetko Popović, Gavrilo Princip, Muhamed Mehmedbašić, Nedeljko Čabrinović, Trifko Grabež, and Vaso Čubrilović) from the Yugoslavist group Mlada Bosna, who had been supplied with arms by the Serbian Black Hand, gathered on the street where the Archduke's motorcade was to pass, with the intention of assassinating him. The political objective of the assassination was to break off Austria-Hungary's South Slav provinces, which Austria-Hungary had annexed from the Ottoman Empire, so they could be combined into a Yugoslavia.
Čabrinović threw a grenade at the car but missed. Some nearby were injured by the blast, but Ferdinand's convoy carried on. The other assassins failed to act as the cars drove past them.
About an hour later, when Ferdinand was returning from a visit at the Sarajevo Hospital with those wounded in the assassination attempt, the convoy took a wrong turn into a street where, by coincidence, Princip stood. With a pistol, Princip shot and killed Ferdinand and his wife Sophie. Although they were reportedly not personally close, the Emperor Franz Joseph was profoundly shocked and upset. The reaction among the people in Austria, however, was mild, almost indifferent. As historian Zbyněk Zeman later wrote, "the event almost failed to make any impression whatsoever. On Sunday and Monday (28 and 29 June), the crowds in Vienna listened to music and drank wine, as if nothing had happened." Nevertheless, the political effect of the murder of the heir to the throne was significant, and was described by historian Christopher Clark on the BBC Radio 4 series Month of Madness as a "9/11 effect, a terrorist event charged with historic meaning, transforming the political chemistry in Vienna."
Expansion of violence in Bosnia and Herzegovina
The Austro-Hungarian authorities encouraged the subsequent anti-Serb riots in Sarajevo, in which Bosnian Croats and Bosniaks killed two Bosnian Serbs and damaged numerous Serb-owned buildings. Violent actions against ethnic Serbs were also organised outside Sarajevo, in other cities in Austro-Hungarian-controlled Bosnia and Herzegovina, Croatia and Slovenia. Austro-Hungarian authorities in Bosnia and Herzegovina imprisoned and extradited approximately 5,500 prominent Serbs, 700 to 2,200 of whom died in prison. A further 460 Serbs were sentenced to death. A predominantly Bosniak special militia known as the Schutzkorps was established and carried out the persecution of Serbs.
The assassination led to a month of diplomatic manoeuvring between Austria-Hungary, Germany, Russia, France and Britain, called the July Crisis. Austria-Hungary correctly believed that Serbian officials (especially the officers of the Black Hand) had been involved in the plot to murder the Archduke, and wanted to finally end Serbian interference in Bosnia. However, the Austrian-Hungarian foreign ministry had no proof of Serbian involvement, and a dossier that it belatedly compiled to make its case against Serbia was riddled with errors. On 23 July, Austria-Hungary delivered to Serbia the July Ultimatum, a series of ten demands that were made intentionally unacceptable, in an effort to provoke a war with Serbia. Serbia decreed general mobilisation on 25 July. Serbia accepted all the terms of the ultimatum except for articles five and six, which demanded that Austrian-Hungarian representatives be allowed to assist in suppressing subversive elements inside Serbia's borders and to participate in the investigation and trial of Serbians linked to the assassination. Following this, Austria broke off diplomatic relations with Serbia and, the next day, ordered a partial mobilisation. Finally, on 28 July 1914, a month after the assassination, Austria-Hungary declared war on Serbia.
On 25 July, Russia, in support of Serbia, declared partial mobilisation against Austria-Hungary. On 30 July, Russia ordered general mobilisation. German Chancellor Bethmann-Hollweg waited until the 31st for an appropriate response, when Germany declared Erklärung des Kriegszustandes, or "Statement on the war status". Kaiser Wilhelm II asked his cousin, Tsar Nicolas II, to suspend the Russian general mobilisation. When he refused, Germany issued an ultimatum demanding its mobilisation be stopped, and a commitment not to support Serbia. Another was sent to France, asking her not to support Russia if it were to come to the defence of Serbia. On 1 August, after the Russian response, Germany mobilised and declared war on Russia. This also led to the general mobilisation in Austria-Hungary on 4 August.
The German government issued demands to France that it remain neutral whilst they decided which deployment plan to implement, it being extremely difficult to change the deployment once it was underway. The modified German Schlieffen Plan, Aufmarsch II West, would deploy 80% of the army in the west, while Aufmarsch I Ost and Aufmarsch II Ost would deploy 60% in the west and 40% in the east. The French did not respond, but sent a mixed message by ordering their troops to withdraw 10 km (6 mi) from the border to avoid any incidents, and at the same time ordered the mobilisation of their reserves. Germany responded by mobilising its own reserves and implementing Aufmarsch II West. The British cabinet decided on 29 July that being a signatory to the 1839 treaty about Belgium did not oblige it to oppose a German invasion of Belgium with military force.
On 1 August, Wilhelm ordered General Helmuth von Moltke the Younger to "march the whole of the ... army to the East" after being informed that Britain would remain neutral if France was not attacked (and, possibly, that her hands might, in any case, be stayed by crisis in Ireland). Moltke told the Kaiser that attempting to redeploy a million men was unthinkable, and that making it possible for the French to attack the Germans "in the rear" would prove disastrous. Yet Wilhelm insisted that the German army should not march into Luxembourg until he received a telegram sent by his cousin George V, who made it clear that there had been a misunderstanding. Eventually the Kaiser told Moltke, "Now you can do what you want."
For years, the French had been aware of intelligence indicating that Germany planned to attack France through Belgium. General Joseph Joffre, chief of staff of the French military from 1911, inquired about the possibility of moving some French troops into Belgium to pre-empt such a move by Germany, but France's civilian leadership rejected this idea. Joffre was told that France would not be the first power to violate Belgian neutrality and that any French move into Belgium could come only after the Germans had already invaded. On 2 August, Germany occupied Luxembourg, and on 3 August declared war on France; on the same day, they sent the Belgian government an ultimatum demanding unimpeded right of way through any part of Belgium, which was refused. Early on the morning of 4 August, the Germans invaded; King Albert ordered his military to resist and called for assistance under the 1839 Treaty of London. Britain demanded Germany comply with the Treaty and respect Belgian neutrality; it declared war on Germany at 19:00 UTC on 4 August 1914 (effective from 23:00), following an "unsatisfactory reply".
Progress of the war
The strategy of the Central Powers suffered from miscommunication. Germany had promised to support Austria-Hungary's invasion of Serbia, but interpretations of what this meant differed. Previously tested deployment plans had been replaced early in 1914, but those had never been tested in exercises. Austro-Hungarian leaders believed Germany would cover its northern flank against Russia. Germany, however, envisioned Austria-Hungary directing most of its troops against Russia, while Germany dealt with France. This confusion forced the Austro-Hungarian Army to divide its forces between the Russian and Serbian fronts.
Austria invaded and fought the Serbian army at the Battle of Cer and Battle of Kolubara beginning on 12 August. Over the next two weeks, Austrian attacks were thrown back with heavy losses, which marked the first major Allied victories of the war and dashed Austro-Hungarian hopes of a swift victory. As a result, Austria had to keep sizeable forces on the Serbian front, weakening its efforts against Russia. Serbia's defeat of the Austro-Hungarian invasion of 1914 has been called one of the major upset victories of the twentieth century. The campaign saw the first use of medical evacuation by the Serbian army in autumn of 1915 and anti-aircraft warfare in the spring of 1915 after an Austrian plane was shot down with ground-to-air fire.
When the war began, the German Order of Battle placed 80% of the army in the West, with the remainder acting as a screening force in the East. The plan was to quickly knock France out of the war, then redeploy to the East and do the same to Russia.
The German offensive in the West was officially titled Aufmarsch II West, but is better known as the Schlieffen Plan, after its original creator. Schlieffen deliberately kept the German left (i.e. its positions in Alsace-Lorraine) weak to lure the French into attacking there, while the majority were allocated to the German right, so as to sweep through Belgium, encircle Paris and trap the French armies against the Swiss border (the French charged into Alsace-Lorraine on the outbreak of war as envisaged by their Plan XVII, thus actually aiding this strategy). However, Schlieffen's successor Moltke grew concerned that the French might push too hard on his left flank. Consequently, as the German Army increased in size in the years leading up to the war, he changed the allocation of forces between the German right and left wings from 85:15 to 70:30. Ultimately, Moltke's changes meant insufficient forces to achieve decisive success and thus unrealistic goals and timings.[dubious ]
The initial German advance in the West was very successful: by the end of August the Allied left, which included the British Expeditionary Force (BEF), was in full retreat; French casualties in the first month exceeded 260,000, including 27,000 killed on 22 August during the Battle of the Frontiers. German planning provided broad strategic instructions, while allowing army commanders considerable freedom in carrying them out at the front; this worked well in 1866 and 1870 but in 1914, von Kluck used this freedom to disobey orders, opening a gap between the German armies as they closed on Paris. The French and British exploited this gap to halt the German advance east of Paris at the First Battle of the Marne from 5 to 12 September and push the German forces back some 50 km (31 mi).
In 1911, the Russian Stavka had agreed with the French to attack Germany within 15 days of mobilisation; this was unrealistic and the two Russian armies that entered East Prussia on 17 August did so without many of their support elements. The Russian Second Army was effectively destroyed at the Battle of Tannenberg on 26–30 August but the Russian advance caused the Germans to re-route their 8th Field Army from France to East Prussia, a factor in Allied victory on the Marne.
By the end of 1914, German troops held strong defensive positions inside France, controlled the bulk of France's domestic coalfields and had inflicted 230,000 more casualties than it lost itself. However, communications problems and questionable command decisions cost Germany the chance of a decisive outcome, and it had failed to achieve the primary objective of avoiding a long, two-front war. This amounted to a strategic defeat; shortly after the Marne, Crown Prince Wilhelm told an American reporter; "We have lost the war. It will go on for a long time but lost it is already."
New Zealand occupied German Samoa (later Western Samoa) on 30 August 1914. On 11 September, the Australian Naval and Military Expeditionary Force landed on the island of Neu Pommern (later New Britain), which formed part of German New Guinea. On 28 October, the German cruiser SMS Emden sank the Russian cruiser Zhemchug in the Battle of Penang. Japan seized Germany's Micronesian colonies and, after the Siege of Tsingtao, the German coaling port of Qingdao on the Chinese Shandong peninsula. As Vienna refused to withdraw the Austro-Hungarian cruiser SMS Kaiserin Elisabeth from Tsingtao, Japan declared war not only on Germany, but also on Austria-Hungary; the ship participated in the defence of Tsingtao where it was sunk in November 1914. Within a few months, the Allied forces had seized all the German territories in the Pacific; only isolated commerce raiders and a few holdouts in New Guinea remained.
Some of the first clashes of the war involved British, French, and German colonial forces in Africa. On 6–7 August, French and British troops invaded the German protectorate of Togoland and Kamerun. On 10 August, German forces in South-West Africa attacked South Africa; sporadic and fierce fighting continued for the rest of the war. The German colonial forces in German East Africa, led by Colonel Paul von Lettow-Vorbeck, fought a guerrilla warfare campaign during World War I and only surrendered two weeks after the armistice took effect in Europe.
Germany attempted to use Indian nationalism and pan-Islamism to its advantage, instigating uprisings in India, and sending a mission that urged Afghanistan to join the war on the side of Central Powers. However, contrary to British fears of a revolt in India, the outbreak of the war saw an unprecedented outpouring of loyalty and goodwill towards Britain. Indian political leaders from the Indian National Congress and other groups were eager to support the British war effort, since they believed that strong support for the war effort would further the cause of Indian Home Rule. The Indian Army in fact outnumbered the British Army at the beginning of the war; about 1.3 million Indian soldiers and labourers served in Europe, Africa, and the Middle East, while the central government and the princely states sent large supplies of food, money, and ammunition. In all, 140,000 men served on the Western Front and nearly 700,000 in the Middle East. Casualties of Indian soldiers totalled 47,746 killed and 65,126 wounded during World War I. The suffering engendered by the war, as well as the failure of the British government to grant self-government to India after the end of hostilities, bred disillusionment and fuelled the campaign for full independence that would be led by Mohandas K. Gandhi and others.
Military tactics developed before World War I failed to keep pace with advances in technology and had become obsolete. These advances had allowed the creation of strong defensive systems, which out-of-date military tactics could not break through for most of the war. Barbed wire was a significant hindrance to massed infantry advances, while artillery, vastly more lethal than in the 1870s, coupled with machine guns, made crossing open ground extremely difficult. Commanders on both sides failed to develop tactics for breaching entrenched positions without heavy casualties. In time, however, technology began to produce new offensive weapons, such as gas warfare and the tank.
After the First Battle of the Marne (5–12 September 1914), Allied and German forces unsuccessfully tried to outflank each other, a series of manoeuvres later known as the "Race to the Sea". By the end of 1914, the opposing forces were left confronting each other along an uninterrupted line of entrenched positions from Alsace to Belgium's North Sea coast. Since the Germans were able to choose where to stand, they normally had the advantage of the high ground; in addition, their trenches tended to be better built, since Anglo-French trenches were initially intended as "temporary," and would only be needed until the breaking of German defences.
Both sides tried to break the stalemate using scientific and technological advances. On 22 April 1915, at the Second Battle of Ypres, the Germans (violating the Hague Convention) used chlorine gas for the first time on the Western Front. Several types of gas soon became widely used by both sides, and though it never proved a decisive, battle-winning weapon, poison gas became one of the most-feared and best-remembered horrors of the war. Tanks were developed by Britain and France and were first used in combat by the British during the Battle of Flers–Courcelette (part of the Battle of the Somme) on 15 September 1916, with only partial success. However, their effectiveness would grow as the war progressed; the Allies built tanks in large numbers, whilst the Germans employed only a few of their own design, supplemented by captured Allied tanks.
Neither side proved able to deliver a decisive blow for the next two years. Throughout 1915–17, the British Empire and France suffered more casualties than Germany, because of both the strategic and tactical stances chosen by the sides. Strategically, while the Germans mounted only one major offensive, the Allies made several attempts to break through the German lines.
In February 1916 the Germans attacked French defensive positions at the Battle of Verdun, lasting until December 1916. The Germans made initial gains, before French counter-attacks returned matters to near their starting point. Casualties were greater for the French, but the Germans bled heavily as well, with anywhere from 700,000 to 975,000 casualties suffered between the two combatants. Verdun became a symbol of French determination and self-sacrifice.
The Battle of the Somme was an Anglo-French offensive of July to November 1916. The opening day of the offensive (1 July 1916) was the bloodiest day in the history of the British Army, suffering 57,470 casualties, including 19,240 dead. The entire Somme offensive cost the British Army some 420,000 casualties. The French suffered another estimated 200,000 casualties and the Germans an estimated 500,000. Gun fire was not the only factor taking lives; the diseases that emerged in the trenches were a major killer on both sides. The living conditions made it so that countless diseases and infections occurred, such as trench foot, shell shock, blindness/burns from mustard gas, lice, trench fever, "cooties" (body lice) and the 'Spanish flu'.
To maintain morale, wartime censors minimised early reports of widespread influenza illness and mortality in Germany, the United Kingdom, France, and the United States. Papers were free to report the epidemic's effects in neutral Spain (such as the grave illness of King Alfonso XIII). This created a false impression of Spain as especially hard hit, thereby giving rise to the pandemic's nickname, "Spanish flu".
Protracted action at Verdun throughout 1916, combined with the bloodletting at the Somme, brought the exhausted French army to the brink of collapse. Futile attempts using frontal assault came at a high price for both the British and the French and led to the widespread French Army Mutinies, after the failure of the costly Nivelle Offensive of April–May 1917. The concurrent British Battle of Arras was more limited in scope, and more successful, although ultimately of little strategic value. A smaller part of the Arras offensive, the capture of Vimy Ridge by the Canadian Corps, became highly significant to that country: the idea that Canada's national identity was born out of the battle is an opinion widely held in military and general histories of Canada.
The last large-scale offensive of this period was a British attack (with French support) at Passchendaele (July–November 1917). This offensive opened with great promise for the Allies, before bogging down in the October mud. Casualties, though disputed, were roughly equal, at some 200,000–400,000 per side.
The years of trench warfare on the Western front achieved no major exchanges of territory and, as a result, are often thought of as static and unchanging. However, throughout this period, British, French, and German tactics constantly evolved to meet new battlefield challenges.
At the start of the war, the German Empire had cruisers scattered across the globe, some of which were subsequently used to attack Allied merchant shipping. The British Royal Navy systematically hunted them down, though not without some embarrassment from its inability to protect Allied shipping. Before the beginning of the war, it was widely understood that Britain held the position of strongest, most influential navy in the world.[unreliable source?] The publishing of the book The Influence of Sea Power upon History by Alfred Thayer Mahan in 1890 was intended to encourage the United States to increase their naval power. Instead, this book made it to Germany and inspired its readers to try to over-power the British Royal Navy. For example, the German detached light cruiser SMS Emden, part of the East Asia Squadron stationed at Qingdao, seized or destroyed 15 merchantmen, as well as sinking a Russian cruiser and a French destroyer. However, most of the German East-Asia squadron—consisting of the armoured cruisers SMS Scharnhorst and Gneisenau, light cruisers Nürnberg and Leipzig and two transport ships—did not have orders to raid shipping and was instead underway to Germany when it met British warships. The German flotilla and Dresden sank two armoured cruisers at the Battle of Coronel, but was virtually destroyed at the Battle of the Falkland Islands in December 1914, with only Dresden and a few auxiliaries escaping, but after the Battle of Más a Tierra these too had been destroyed or interned.
Soon after the outbreak of hostilities, Britain began a naval blockade of Germany. The strategy proved effective, cutting off vital military and civilian supplies, although this blockade violated accepted international law codified by several international agreements of the past two centuries. Britain mined international waters to prevent any ships from entering entire sections of ocean, causing danger to even neutral ships. Since there was limited response to this tactic of the British, Germany expected a similar response to its unrestricted submarine warfare.
The Battle of Jutland (German: Skagerrakschlacht, or "Battle of the Skagerrak") in May/June 1916 developed into the largest naval battle of the war. It was the only full-scale clash of battleships during the war, and one of the largest in history. The Kaiserliche Marine's High Seas Fleet, commanded by Vice Admiral Reinhard Scheer, fought the Royal Navy's Grand Fleet, led by Admiral Sir John Jellicoe. The engagement was a stand off, as the Germans were outmanoeuvred by the larger British fleet, but managed to escape and inflicted more damage to the British fleet than they received. Strategically, however, the British asserted their control of the sea, and the bulk of the German surface fleet remained confined to port for the duration of the war.
German U-boats attempted to cut the supply lines between North America and Britain. The nature of submarine warfare meant that attacks often came without warning, giving the crews of the merchant ships little hope of survival. The United States launched a protest, and Germany changed its rules of engagement. After the sinking of the passenger ship RMS Lusitania in 1915, Germany promised not to target passenger liners, while Britain armed its merchant ships, placing them beyond the protection of the "cruiser rules", which demanded warning and movement of crews to "a place of safety" (a standard that lifeboats did not meet). Finally, in early 1917, Germany adopted a policy of unrestricted submarine warfare, realising the Americans would eventually enter the war. Germany sought to strangle Allied sea lanes before the United States could transport a large army overseas, but after initial successes eventually failed to do so.
The U-boat threat lessened in 1917, when merchant ships began travelling in convoys, escorted by destroyers. This tactic made it difficult for U-boats to find targets, which significantly lessened losses; after the hydrophone and depth charges were introduced, accompanying destroyers could attack a submerged submarine with some hope of success. Convoys slowed the flow of supplies, since ships had to wait as convoys were assembled. The solution to the delays was an extensive program of building new freighters. Troopships were too fast for the submarines and did not travel the North Atlantic in convoys. The U-boats had sunk more than 5,000 Allied ships, at a cost of 199 submarines.
World War I also saw the first use of aircraft carriers in combat, with HMS Furious launching Sopwith Camels in a successful raid against the Zeppelin hangars at Tondern in July 1918, as well as blimps for antisubmarine patrol.
Faced with Russia in the east, Austria-Hungary could spare only one-third of its army to attack Serbia. After suffering heavy losses, the Austrians briefly occupied the Serbian capital, Belgrade. A Serbian counter-attack in the Battle of Kolubara succeeded in driving them from the country by the end of 1914. For the first ten months of 1915, Austria-Hungary used most of its military reserves to fight Italy. German and Austro-Hungarian diplomats, however, scored a coup by persuading Bulgaria to join the attack on Serbia. The Austro-Hungarian provinces of Slovenia, Croatia and Bosnia provided troops for Austria-Hungary in the fight with Serbia, Russia and Italy. Montenegro allied itself with Serbia.
Bulgaria declared war on Serbia on 12 October 1915 and joined in the attack by the Austro-Hungarian army under Mackensen's army of 250,000 that was already underway. Serbia was conquered in a little more than a month, as the Central Powers, now including Bulgaria, sent in 600,000 troops total. The Serbian army, fighting on two fronts and facing certain defeat, retreated into northern Albania. The Serbs suffered defeat in the Battle of Kosovo. Montenegro covered the Serbian retreat towards the Adriatic coast in the Battle of Mojkovac in 6–7 January 1916, but ultimately the Austrians also conquered Montenegro. The surviving Serbian soldiers were evacuated by ship to Greece. After conquest, Serbia was divided between Austro-Hungary and Bulgaria.
In late 1915, a Franco-British force landed at Salonica in Greece to offer assistance and to pressure its government to declare war against the Central Powers. However, the pro-German King Constantine I dismissed the pro-Allied government of Eleftherios Venizelos before the Allied expeditionary force arrived. The friction between the King of Greece and the Allies continued to accumulate with the National Schism, which effectively divided Greece between regions still loyal to the king and the new provisional government of Venizelos in Salonica. After intense negotiations and an armed confrontation in Athens between Allied and royalist forces (an incident known as Noemvriana), the King of Greece resigned and his second son Alexander took his place; Greece officially joined the war on the side of the Allies in June 1917.
The Macedonian front was initially mostly static. French and Serbian forces retook limited areas of Macedonia by recapturing Bitola on 19 November 1916 following the costly Monastir Offensive, which brought stabilisation of the front.
Serbian and French troops finally made a breakthrough in September 1918 in the Vardar Offensive, after most of the German and Austro-Hungarian troops had been withdrawn. The Bulgarians were defeated at the Battle of Dobro Pole, and by 25 September British and French troops had crossed the border into Bulgaria proper as the Bulgarian army collapsed. Bulgaria capitulated four days later, on 29 September 1918. The German high command responded by despatching troops to hold the line, but these forces were far too weak to re-establish a front.
The disappearance of the Macedonian front meant that the road to Budapest and Vienna was now opened to Allied forces. Hindenburg and Ludendorff concluded that the strategic and operational balance had now shifted decidedly against the Central Powers and, a day after the Bulgarian collapse, insisted on an immediate peace settlement.
The Ottomans threatened Russia's Caucasian territories and Britain's communications with India via the Suez Canal. As the conflict progressed, the Ottoman Empire took advantage of the European powers' preoccupation with the war and conducted large-scale ethnic cleansing of the indigenous Armenian, Greek, and Assyrian Christian populations, known as the Armenian Genocide, Greek Genocide, and Assyrian Genocide.
The British and French opened overseas fronts with the Gallipoli (1915) and Mesopotamian campaigns (1914). In Gallipoli, the Ottoman Empire successfully repelled the British, French, and Australian and New Zealand Army Corps (ANZACs). In Mesopotamia, by contrast, after the defeat of the British defenders in the Siege of Kut by the Ottomans (1915–16), British Imperial forces reorganised and captured Baghdad in March 1917. The British were aided in Mesopotamia by local Arab and Assyrian tribesmen, while the Ottomans employed local Kurdish and Turcoman tribes.
Further to the west, the Suez Canal was defended from Ottoman attacks in 1915 and 1916; in August, a German and Ottoman force was defeated at the Battle of Romani by the ANZAC Mounted Division and the 52nd (Lowland) Infantry Division. Following this victory, an Egyptian Expeditionary Force advanced across the Sinai Peninsula, pushing Ottoman forces back in the Battle of Magdhaba in December and the Battle of Rafa on the border between the Egyptian Sinai and Ottoman Palestine in January 1917.
Russian armies generally had success in the Caucasus campaign. Enver Pasha, supreme commander of the Ottoman armed forces, was ambitious and dreamed of re-conquering central Asia and areas that had been lost to Russia previously. He was, however, a poor commander. He launched an offensive against the Russians in the Caucasus in December 1914 with 100,000 troops, insisting on a frontal attack against mountainous Russian positions in winter. He lost 86% of his force at the Battle of Sarikamish.
The Ottoman Empire, with German support, invaded Persia (modern Iran) in December 1914 in an effort to cut off British and Russian access to petroleum reservoirs around Baku near the Caspian Sea. Persia, ostensibly neutral, had long been under the spheres of British and Russian influence. The Ottomans and Germans were aided by Kurdish and Azeri forces, together with a large number of major Iranian tribes, such as the Qashqai, Tangistanis, Luristanis, and Khamseh, while the Russians and British had the support of Armenian and Assyrian forces. The Persian Campaign was to last until 1918 and end in failure for the Ottomans and their allies. However, the Russian withdrawal from the war in 1917 led to Armenian and Assyrian forces, who had hitherto inflicted a series of defeats upon the forces of the Ottomans and their allies, being cut off from supply lines, outnumbered, outgunned and isolated, forcing them to fight and flee towards British lines in northern Mesopotamia.
General Yudenich, the Russian commander from 1915 to 1916, drove the Turks out of most of the southern Caucasus with a string of victories. During the 1916 campaign, the Russians defeated the Turks in the Erzurum Offensive, also occupying Trabzon. In 1917, Russian Grand Duke Nicholas assumed command of the Caucasus front. Nicholas planned a railway from Russian Georgia to the conquered territories, so that fresh supplies could be brought up for a new offensive in 1917. However, in March 1917 (February in the pre-revolutionary Russian calendar), the Tsar abdicated in the course of the February Revolution, and the Russian Caucasus Army began to fall apart.
The Arab Revolt, instigated by the Arab bureau of the British Foreign Office, started June 1916 with the Battle of Mecca, led by Sherif Hussein of Mecca, and ended with the Ottoman surrender of Damascus. Fakhri Pasha, the Ottoman commander of Medina, resisted for more than two and half years during the Siege of Medina before surrendering in January 1919.
The Senussi tribe, along the border of Italian Libya and British Egypt, incited and armed by the Turks, waged a small-scale guerrilla war against Allied troops. The British were forced to dispatch 12,000 troops to oppose them in the Senussi Campaign. Their rebellion was finally crushed in mid-1916.
Total Allied casualties on the Ottoman fronts amounted 650,000 men. Total Ottoman casualties were 725,000 (325,000 dead and 400,000 wounded).
Italy had been allied with the German and Austro-Hungarian Empires since 1882 as part of the Triple Alliance. However, the nation had its own designs on Austro-Hungarian territory in Trentino, the Austrian Littoral, Fiume (Rijeka) and Dalmatia. Rome had a secret 1902 pact with France, effectively nullifying its part in the Triple Alliance; Italy secretly agreed with France to remain neutral if the latter was attacked by Germany. At the start of hostilities, Italy refused to commit troops, arguing that the Triple Alliance was defensive and that Austria-Hungary was an aggressor. The Austro-Hungarian government began negotiations to secure Italian neutrality, offering the French colony of Tunisia in return. The Allies made a counter-offer in which Italy would receive the Southern Tyrol, Austrian Littoral and territory on the Dalmatian coast after the defeat of Austria-Hungary. This was formalised by the Treaty of London. Further encouraged by the Allied invasion of Turkey in April 1915, Italy joined the Triple Entente and declared war on Austria-Hungary on 23 May. Fifteen months later, Italy declared war on Germany.
The Italians had numerical superiority, but this advantage was lost, not only because of the difficult terrain in which the fighting took place, but also because of the strategies and tactics employed. Field Marshal Luigi Cadorna, a staunch proponent of the frontal assault, had dreams of breaking into the Slovenian plateau, taking Ljubljana and threatening Vienna.
On the Trentino front, the Austro-Hungarians took advantage of the mountainous terrain, which favoured the defender. After an initial strategic retreat, the front remained largely unchanged, while Austro-Hungarian Kaiserjäger, Kaiserschützen and Standschützen engaged Italian Alpini in bitter hand-to-hand combat throughout the summer. In the Alpine and Dolomite fronts, the main battle line led through rock and ice and often to an altitude of over 3000m. The soldiers were threatened not only by the enemy but especially in winter by the forces of nature and the difficult supply. The fighting led to the formation of special units with mountain guides and new combat tactics. The Austro-Hungarians counterattacked in the Altopiano of Asiago, towards Verona and Padua, in the spring of 1916 (Strafexpedition), but made little progress and were defeated by the Italians.
Beginning in 1915, the Italians under Cadorna mounted eleven offensives on the Isonzo front along the Isonzo (Soča) River, northeast of Trieste. Of these eleven offensives, five were won by Italy, three remained inconclusive, and the other three were repelled by the Austro-Hungarians, who held the higher ground. In the summer of 1916, after the Battle of Doberdò, the Italians captured the town of Gorizia. After this victory, the front remained static for over a year, despite several Italian offensives, centred on the Banjšice and Karst Plateau east of Gorizia.
The Central Powers launched a crushing offensive on 26 October 1917, spearheaded by the Germans, and achieved a victory at Caporetto (Kobarid). The Italian Army was routed and retreated more than 100 kilometres (62 mi) to reorganise. The new Italian chief of staff, Armando Diaz, ordered the Army to stop their retreat and defend the Monte Grappa summit, where fortified defences were constructed; the Italians repelled the Austro-Hungarian and German Army, and stabilised the front at the Piave River. Since the Italian Army had suffered heavy losses in the Battle of Caporetto, the Italian Government ordered conscription of the so-called '99 Boys (Ragazzi del '99): all males born in 1899 and prior, who were 18 years old or older. In 1918, the Austro-Hungarians failed to break through in a series of battles on the Piave and were finally decisively defeated in the Battle of Vittorio Veneto in October. On 1 November, the Italian Navy destroyed much of the Austro-Hungarian fleet stationed in Pula, preventing it from being handed over to the new State of Slovenes, Croats and Serbs. On 3 November, the Italians invaded Trieste from the sea. On the same day, the Armistice of Villa Giusti was signed. By mid-November 1918, the Italian military occupied the entire former Austrian Littoral and had seized control of the portion of Dalmatia that had been guaranteed to Italy by the London Pact. By the end of hostilities in November 1918, Admiral Enrico Millo declared himself Italy's Governor of Dalmatia. Austria-Hungary surrendered on 11 November 1918.
Romania had been allied with the Central Powers since 1882. When the war began, however, it declared its neutrality, arguing that because Austria-Hungary had itself declared war on Serbia, Romania was under no obligation to join the war. On 4 August 1916, Romania and the Entente signed the Political Treaty and Military Convention, that established the coordinates of Romania's participation in the war. In return, it received the Allies' formal sanction for Transylvania, Banat and other territories of Austria-Hungary to be annexed to Romania. The action had large popular support. On 27 August 1916, the Romanian Army launched an attack against Austria-Hungary, with limited Russian support. The Romanian offensive was initially successful in Transylvania, but a Central Powers counterattack drove them back. As a result of the Battle of Bucharest, the Central Powers occupied Bucharest on 6 December 1916. Fighting in Moldova continued in 1917, but Russian withdrawal from the war in late 1917 as a result of the October Revolution meant that Romania was forced to sign an armistice with the Central Powers on 9 December 1917.
In January 1918, Romanian forces established control over Bessarabia as the Russian Army abandoned the province. Although a treaty was signed by the Romanian and Bolshevik Russian governments following talks between 5 and 9 March 1918 on the withdrawal of Romanian f