A mass killing, as defined by a genocide scholar Ervin Staub, is "killing members of a group without the intention to eliminate the whole group or killing large numbers of people without a precise definition of group membership".[nb 1] This term is used by a number of genocide scholars because the term "genocide" (its strict definition) does not cover mass killing events when no specific ethnic or religious group is targeted, and when perpetrators are not intended to eliminate of the whole group or its significant part. This article primarily discusses different models used by genocide scholars to explain and predict the onset of mass killing events.
According to Weiss-Wendt, any attempts to develop a universally accepted terminology describing mass killings of non-combatants was a complete failure Below are listed the terms used by genocide scholars to describe mass killings.
- Mass killing
- Referencing earlier definitions, [nb 2] Joan Esteban, Massimo Morelli and Dominic Rohner have defined mass killings as "the killings of substantial numbers of human beings, when not in the course of military action against the military forces of an avowed enemy, under the conditions of the essential defenselessness and helplessness of the victims".  The term has been defined by Benjamin Valentino as "the intentional killing of a massive number of noncombatants", where a "massive number" is defined as at least 50,000 intentional deaths over the course of five years or less.  This is the most accepted quantitative minimum threshold for the term.    [nb 3]
- Under the Genocide Convention, the crime of genocide generally applies to mass murder of ethnic rather than political or social groups. Protection of political groups was eliminated from the UN resolution after a second vote, because many states  anticipated that clause to apply unneeded limitations to their right to suppress internal disturbances.  Genocide is also a popular term for mass political killing, which is studied academically as democide and politicide. 
- The term "politicide" is used to describe the killing of groups that would not otherwise be covered by the Genocide Convention.  Barbara Harff studies "genocide and politicide", sometimes shortened as geno-politicide, to include the mass killing of political, economic, ethnic and cultural groups. 
R. J. Rummel defines democide as "the intentional killing of an unarmed or disarmed person by government agents acting in their authoritative capacity and pursuant to government policy or high command".
 According to him, this definition covers a wide range of deaths, including forced labor and concentration camp victims; killings by "unofficial" private groups; extrajudicial summary killings; and mass deaths in deliberate famines, as well as killings by
de facto governments, e.g. civil war killings.
Rummel's "democide" concept is very similar to "geno-politicide", however there are two important differences. First, an important prerequisite for geno-politicide is government's intent to destroy a specific group. In contrast, "democide" deals with wider range of cases, including the cases when governments are engaged in random killing either directly or due to the acts of criminal omission and neglect.
Second, whereas some lower threshold exists for a killing event to be considered "geno-politicide" (Valentino uses 50,000/five years, other authors use lower threshold), there is no low threshold for democide, which covers any murder of any number of persons by any government.
- Proposed by Michael Mann to describe the "intended mass killing of entire social classes".  [nb 4]
Dispossessive vs coercive mass killings
Benjamen Valentino, who sees ruler's motives as the key factor explaining the onset of mass killings, outlines two major category of mass killings, dispossessive mass killings and coercive mass killings. The first category included ethnic cleansing, killings that accompany agrarian reforms in some states led by communists, mass killings during colonial expansion, etc. The second category includes mass killings during counter-guerilla warfare, killings during the Axis imperialist conquests during the World War II, etc. Although Valentino does not consider ideology or regime type as an important factor that explains mass killings, he outlines communist mass killings as a subtype of dispossessive mass killings, which is considered as a complication of original theory his book is based on.
Global databases of mass killings
Two global databases of mass killings are currently available. The first compilation, by Rudolph Rummel, covers a time period from the beginning of the 20th century till 1977, and the second compilation, by Barbara Harff, combines all mass killing events since 1955. The Harff database is the most frequently used by genocide scholars. These data are intended mostly for statistical analysis of mass killings in attempt to identify the best predictors for their onset. According to Harff, these data are not necessarily the most accurate for a given country, since some sources are general genocide scholars and not experts on local history. A comparative analysis of these two databases revealed a significant difference between the figures of killed per years and low correlation between Rummel's and Harff's data sets. Tomislav Dulić criticized Rummel's generally higher numbers as arising from flaws in Rummel's statistical methodology.
|Country and date||Start||End||Nature of episode||Estimated number of victims||Related articles|
|Sudan||Oct 1956||Mar 1972||Politicide with communal victims||400,000–600,000||First Sudanese Civil War|
|South Vietnam||Jan 1965||Apr 1975||Politicide||400,000–500,000||South Vietnam|
|China||Mar 1959||Dec 1959||Genocide and politicide||65,000||1959 Tibetan uprising|
|Iraq||Jun 1963||Mar 1975||Politicide with communal victims||30,000–60,000||Ba'athist Iraq|
|Algeria||Jul 1962||Dec 1962||Politicide||9,000–30,000|
|Rwanda||Dec 1963||Jun 1964||Politicide with communal victims||12,000–20,000|
|Congo-Kinshasa||Feb 64||Jan 1965||Politicide||1,000–10,000|
|Burundi||Oct 1965||Dec 1973||Politicide with communal victims||140,000|
|Indonesia||Nov 1965||Jul 1966||Genocide and politicide||500,000–1,000,000||Indonesian mass killings of 1965–1966|
|China||May 1966||Mar 1975||Politicide||400,000–850,000|
|Guatemala||Jul 1978||Dec 1996||Politicide and genocide||60,000–200,000||Guatemalan genocide|
|Pakistan||Mar 1971||Dec 1971||Politicide with communal victims||1,000,000–3,000,000|
|Uganda||Dec 1972||Apr 1979||Politicide and genocide||50,000–400,000||Genocides in central Africa|
|Philippines||Sep 1972||Jun 1976||Politicide with communal victims||60,000|
|Pakistan||Feb 1973||Jul 1977||Politicide with communal victims||5,000–10,000|
|Chile||Sep 1973||Dec 1976||Politicide||5,000–10,000|
|Angola||Nov 1975||2001||Politicide by UNITA and government forces||500,000|
|Cambodia||Apr 1975||Jan 1979||Politicide and genocide||1,900,000–3,500,000||Cambodian genocide|
|Indonesia||Dec 1975||Jul 1992||Politicide with communal victims||100,000–200,000|
|Argentina||Mar 1976||Dec 1980||Politicide||9,000–20,000|
|Ethiopia||Jul 1976||Dec 1979||Politicide||10,000|
|Congo-Kinshasa||Mar 1977||Dec 1979||Politicide with communal victims||3,000–4,000|
|Afghanistan||Apr 1978||Apr 1992||Politicide||1,800,000|
|Burma||Jan 1978||Dec 1978||Genocide||5,000|
|El. Salvador||Jan 1980||Dec 1989||Politicide||40,000–60,000|
|Uganda||Dec 1980||Jan 1986||Politicide and genocide||200,000-500,000||Genocides in central Africa|
|Syria||Mar 1981||Feb 1982||Politicide||5,000–30,000|
|Iran||Jun 1981||Dec 1992||Politicide and genocide||10,000–20,000||Casualties of the Iranian Revolution, 1988 executions of Iranian political prisoners|
|Sudan||Sep 1983||?||Politicide with communal victims||2,000,000|
|Iraq||Mar 1988||Jun 1991||Politicide with communal victims||180,000|
|Somalia||May 1988||Jan 1991||Politicide with communal victims||15,000–50,000|
|Burundi||1988||1988||Genocide||5,000–20,000||Hutu massacres of 1988|
|Sri Lanka||Sep 1989||Jan 1990||Politicide||13,000–30,000|
|Bosnia||May 1992||Nov 1995||Genocide||225,000||Bosnian genocide|
|Burundi||Oct 1993||May 1994||Genocide||50,000||Burundian genocides|
|Rwanda||Apr 1994||Jul 1994||Genocide||500,000–1,000,000||Rwandan genocide|
|Serbia||Dec 1998||Jul 1999||Politicide with communal victims||10,000|
Explanation of the onset of mass killings
The term "mass killing" was proposed by genocide scholars in attempts to collect a uniform global database of genocidal events and identify statistical models for prediction of onset of mass killings.
Frank Wayman and Atsushi Tago use the term "mass killing" as defined by Valentino, and they concluded that, even with a lower threshold (10,000 killed per year, 1,000 killed per year, or even 1), "autocratic regimes, especially communist, are prone to mass killing generically, but not so strongly inclined (i.e. not statistically significantly inclined) toward geno-politicide".