A civil war is a war between a state and domestic political actors that are in control of some part of the territory claimed by the state. It is high-intensity conflict, often involving regular armed forces, that is sustained, organized and large-scale. Civil wars result in large numbers of casualties and the expenditure of large amounts of resource. A civil war involves two-sided violence; for example, a massacre of civilians by the state is not a civil war. Similarly, less intense forms of societal conflict, such as riots or social movements, are excluded from the definition.
The Geneva Conventions do not specifically define the term 'civil war'. They do, however, describe the criteria that separate any act committed by force of arms (anarchy, terrorism, or plain banditry) from those qualifying as 'armed conflict not of an international character', which includes civil wars. Among those conditions listed are these four basic requirements.
- The party in revolt must be in possession of a part of the national territory.
- The insurgent civil authority must exercise de facto authority over the population within the determinate portion of the national territory.
- The insurgents must have some amount of recognition as a belligerent.
- The legal Government is "obliged to have recourse to the regular military forces against insurgents organized as military."
The International Committee of the Red Cross (ICRC) further clarified Article 9 of the Geneva Convention. They stated that the nature of these armed conflicts, not of an international character "generally refer to conflicts with armed forces on either side which are in many respects similar to an international war, but take place within the confines of a single country."
The U.S. Military has adopted the principles set by the Diplomatic Conference of Geneva for their definition of civil war. However, it adds a fifth requirement for "identifiable regular armed forces".
A civil war is "a violent conflict within a country fought by organized groups that aim to take power at the center or in a region, or to change government policies". Scholars use two specific criteria to determine a civil war: the warring groups must be from the same country and fighting for control of the political center, control over a separatist state or to force a major change in policy. Another criterion, used by some academics, is that at least 1,000 people must have been killed in total, with at least 100 from each side.