This entry inspired by a recent comment I read from a theist who argued that individuals following “atheistic philosophies were responsible for more deaths than any other group in human history”. Obviously he was referring to the millions who have died as a result of communism in the 20th century. I, of course, reject this notion that there is even such a thing as an “atheistic philosophy"; furthermore I do I consider communism to be synonymous with atheism. For the sake of this discussion, we're going to grant that communism = atheism and make a comparison based solely upon 20th century statistics.
These are just 20th Century conflicts involving 150,000+ fatalities (per http://users.erols.com/mwhite28/warstat1.htm ). There are just too many to include conflicts involving less that 150,00 fatalities..
Deaths inflicted by predominately religious nations in the 20th century
First World War (1914-18): 15 000 000
Congo Free State (1886-1908): 8 000 000
Armenian Massacres (1915-23): 1 500 000
Rwanda and Burundi (1959-95): 1 350 000
Nigeria (1966-70): 1 000 000
Iran-Iraq War (1980-88): 1 000 000
Sudan (1983 et seq.): 1 900 000
Kinshasa Congo (1998 et seq.): 3 800 00
Brazil (1900 et seq.): 500 000
Abyssinian Conquest (1935-41): 400 000
First Indochina War (1945-54): 400 000
Uganda, Idi Amin's regime (1972-79): 300 000
East Timor, Conquest by Indonesia (1975-99): 200 000
Lebanon (1975-90): 150 000
Iraq, Saddam Hussein (1979-2003): 300 000
Kurdistan (1980s, 1990s): 300 000
Bosnia and Herzegovina (1992-95): 175 000
Somalia (1991 et seq.): 400 000
Zaire (Dem. Rep. Congo), Civil War (1997) 250,000
Total: 43,062,000
Deaths inflicted by predominately communist/socialist/"atheist" factions:
Soviet Union, Stalin's regime (1924-53): 20 000 000
People's Republic of China, Mao Zedong's regime (1949-1975): 40 000 000
Cambodia, Khmer Rouge (1975-1978): 1 650 000
Mozambique (1975-1992): 1 000 000
Russo-Finnish War (1939-1940): 150 000
Vietnam, post-war Communist regime (1975 et seq.): 430,000
Cambodian Civil War (1978-91): 225 000
Yugoslavia, Tito's Regime (1944-80): 200 000
Total: 64,405,000
Note: These are the total deaths inflicted by communist regimes upon it's citizenry; includes deaths resulting from disease and starvation. Some estimate that this total is lower than the combined total of Native America's killed in the conquest of the Americas and Africans killed in the slave trade (both inflicted predominately by Christians).
Death's suffered in war's involving both “atheist” and “religious” factions:
Second World War (1937-45): 55 000 000
Russian Civil War (1917-22): 9 000 000
Chinese Civil War (1945-49): 2 500 000
Mexican Revolution (1910-20): 1 000 000
Korean War (1950-53): 2 800 000
Second Indochina War (1960-75): 3 500 000
Afghanistan (1979-2001): 1 800 000
Spanish Civil War (1936-39) 365 00
Greek Civil War (1943-49): 158 000
Total: 76,123,000
Note: The significant majority of these dead were communist killed by predominately religious nations. As it turns out, communist tend to die in far greater numbers than capitalists. Many theists wish to blame 100% of these deaths on communists, but this quite simply isn't justifiable. In many instances, the communists were attempting to overthrow overtly evil tyrannies. Of the WW II deaths, only 10,000,000 were inflicted by the Soviets, many in the act of defending themselves from Nazi aggression; meaning that the remaining 45,000,000 were inflicted by predominately religious nations.
Ultimately the deaths inflicted by conflicts in the 20th century are pretty evenly divided between predominately religious and communist nations. Without a doubt, communism was a scourge of the 20th century, though it's understandable why many people sought to replace the tyrannies they lived under with communist regimes...sadly, they often merely replaced one tyranny with another. Of course, it's a total farce to suggest that “practitioners of atheistic philosophies” (still no idea what an “atheistic philosophy” might be) have lead to more deaths than any other group combined. I would argue (and the facts would easily back me on this) that predominately religious nations as a group have massively inflicted far more death in human history than “atheistic philosophies” particularly if the tales of the Old Testament are true...but this is nit picking. Now, the 20th century enjoyed massively higher populations than did an other century (in fact the majority of human to have ever lived did so during the 20th century), so it's not surprising to see that the wars fought during that century inflicted far more casualties (in fact the 55,000,000 killed in WWII alone would have been 1/4th the human population at the time of Jesus). Furthermore, during the twenty century, the devices of war were far more refined and effective...it was just much easier to kill a lot of people in the 20th than any other time. So in most ways, comparing the war dead of the 20th century to other centuries is an extremely unbalanced comparison; however even when you do you still find that predominately religious nations killed about as many people as non-religious nations. The main difference is that almost all non-believers view the past actions of communist regimes as despicable while many theists dream of holy wars to come.