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.
Civil wars since the end of World War II have lasted on average just over four years, a dramatic rise from the one-and-a-half year average of the 1900-1944 period. While the rate of emergence of new civil wars has been relatively steady since the mid-1800s, the increasing length of those wars resulted in increasing numbers of wars ongoing at any one time. For example, there were no more than five civil wars underway simultaneously in the first half of the twentieth century, while over 20 concurrent civil wars were occurring at the end of the Cold War, before a significant decrease as conflicts strongly associated with the superpower rivalry came to an end. Since 1945, civil wars have resulted in the deaths of over 25 million people, as well as the forced displacement of millions more. Civil wars have further resulted in economic collapse; Burma (Myanmar), Uganda and Angola are examples of nations that were considered to have promising futures before being engulfed in civil wars.
Scholars of war divide theories on the causes of civil war into either greed versus grievance. Roughly stated: are conflicts caused by who people are, whether that be defined in terms of ethnicity, religion or other social affiliation, or do conflicts begin because it is in the economic best interests of individuals and groups to start them? Scholarly analysis supports the conclusion that economic and structural factors are more important than those of identity in predicting occurrences of civil war.
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 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. The Correlates of War, a dataset widely used by scholars of conflict, classifies civil wars as having over 1000 war-related casualties per year of conflict. This rate is a small fraction of the millions killed in the Second Sudanese Civil War and Cambodian Civil War, for example, but excludes several highly publicized conflicts, such as The Troubles of Northern Ireland and the struggle of the African National Congress in Apartheid-era South Africa. Based on the 1000 casualties per year criterion, there were 213 civil wars from 1816 to 1997, 104 of which occurred from 1944 to 1997.
A high proportion of primary commodities in national exports significantly increases the risk of a conflict. A country at "peak danger", with commodities comprising 32% of gross domestic product, has a 22% of falling into civil war in a given five-year period, while a country with no primary commodity exports has a 1% risk. When disaggregated, only petroleum and non-petroleum groupings showed different results: a country with relatively low levels of dependence on petroleum exports is at slightly less risk, while a high-level of dependence on oil as an export results in slightly more risk of a civil war than national dependence on another primary commodity. The authors of the study interpreted this as being the result of the ease by which primary commodities may be extorted or captured compared to other forms of wealth, e.g. it is easy to capture and control the output of a gold mine or oil field compared to a sector of garment manufacturing or hospitality services.
A second source of finance is national diasporas, which can fund rebellions and insurgencies from abroad. The study found that statistically switching the size of a country's diaspora from the smallest found in the study to the largest resulted in a sixfold increase in the chance of a civil war.
Opportunity cost of rebellion Higher male secondary school enrollment, per capita income and economic growth rate all had significant effects on reducing the chance of civil war. Specifically, a male secondary school enrollment 10% above the average reduced the chance of a conflict by about 3%, while a growth rate 1% higher than the study average resulted in a decline in the chance of a civil war of about 1%. The study interpreted these three factors as proxies for earnings foregone by rebellion, and therefore that lower foregone earnings encourages rebellion. Phrased another way: young males (who make up the vast majority of combatants in civil wars) are less likely to join a rebellion if they are getting an education and/or have a comfortable salary, and can reasonably assume that they will prosper in the future.
Low per capita income has been proposed as a cause for grievance, prompting armed rebellion. However, for this to be true, one would expect economic inequality to also be a significant factor in rebellions, which it is not. The study therefore concluded that the economic model of opportunity cost better explained the findings.Military advantage High levels of population dispersion and, to a lesser extent, the presence of mountainous terrain increased the chance of conflict. Both of these factors favor rebels, as a population dispersed outward toward the borders is harder to control than one concentrated in a central region, while mountains offer terrain where rebels can seek sanctuary.Grievance
Most proxies for "grievance" - the theory that civil wars begin because of issues of identity, rather than economics - were statistically insignificant, including economic equality, political rights, ethnic polarization and religious fractionalization. Only ethnic dominance, the case where the largest ethnic group comprises a majority of the population, increased the risk of civil war. A country characterized by ethnic dominance has nearly twice the chance of a civil war. However, the combined effects of ethnic and religious fractionalization, i.e. the more chance that any two randomly chosen people will be from separate ethnic or religious groups the less chance of a civil war, were also significant and positive, as long as the country avoided ethnic dominance. The study interpreted this as stating that minority groups are more likely to rebel if they feel that they are being dominated, but that rebellions are more likely to occur the more homogeneous the population and thus more cohesive the rebels. These two factors may thus be seen as mitigating each other in many cases.Population size The various factors contributing to the risk of civil war rise increase with population size. The risk of a civil war rises approximately proportionately with the size of a country's population.Time The more time that has elapsed since the last civil war, the less likely it is that a conflict will recur. The study had two possible explanations for this: one opportunity-based and the other grievance-based. The elapsed time may represent the depreciation of whatever capital the rebellion was fought over and thus increase the opportunity cost of restarting the conflict. Alternatively, elapsed time may represent the gradual process of healing of old hatreds. The study found that the presence of diaspora substantially reduced the positive effect of time, as the funding from diasporas offsets the depreciation of rebellion-specific capital.
The modern history of civil wars may be divided into the pre-nineteenth century, nineteenth century to early twentieth century, and late twentieth century. In nineteenth century Europe, the length of civil wars fell significantly, largely due to the nature of the conflicts as battles for the power center of the state, the strength of centralized governments, and the normally quick and decisive intervention by other states to support the government. Following World War II the duration of civil wars grew past the norm of the pre-nineteenth century, largely due to weakness of the many postcolonial states and the intervention by major powers on both sides of conflict. The most obvious commonality to civil wars are that they occur in fragile states.
The power of non-state actors resulted in a lower value placed on sovereignty in the eighteenth and nineteenth century, which further reduced the number of civil wars. For example, the pirates of the Barbary Coast were recognized as de facto states because of their military power. The Barbary pirates thus had no need to rebel against the Ottoman Empire, who were their nominal state government, to gain recognition for their sovereignty. Conversely, states such as Virginia and Massachusetts in the United States of America did not have sovereign status, but had significant political and economic independence coupled with weak federal control, reducing the incentive to secede.
The two major global ideologies, monarchism and democracy, led to several civil wars. However, a bi-polar world, divided between the two ideologies, did not develop, largely due the dominance of monarchists through most of the period. The monarchists would thus normally intervene in other countries to stop democratic movements taking control and forming democratic governments, which were seen by monarchists as being both dangerous and unpredictable. The Great Powers, defined in the 1815 Congress of Vienna as the United Kingdom, Habsburg Austria, Prussia, France, and Russia, would frequently coordinate interventions in other nations' civil wars, nearly always on the side of the incumbent government. Given the military strength of the Great Powers, these interventions were nearly always decisive and quickly ended the civil wars.
There were several exceptions from the general rule of quick civil wars during this period. The American Civil War (1861-1865) was unusual for at least two reasons: it was fought around regional identities, rather than political ideologies, and it was ended through a war of attrition, rather than over a decisive battle over control of the capital, as was the norm. The Spanish Civil War (1936-1939) was exceptional because both sides of the war received support from intervening great powers: Germany, Italy and Portugal supported opposition leader Francisco Franco, while France and Russia supported the government.