War is organized and often prolonged conflict carried out by state or non-state actors. It is characterized by extreme violence, social disruption, and attempted economic destruction. It is a form of collective political violence or intervention. The absence of war is known as peace. It is disputed whether warfare is inescapable or inevitable, with some arguing that some human societies do not engage in warfare. The deadliest wars in terms of cumulative deaths include:

• WWII (Second World War, 1939-1945), with 60-85 million deaths
• Mongol conquests (13th century), with 60 million deaths
• Taiping Rebellion (1850-1864), with 40 million deaths
• WWI (World War 1, 1914-1918), with 39 million deaths
• An Shi Rebellion (755-763), with 36 million deaths
• Second Sino-Japanese War (1937-1945), with 20 million deaths
• Conquests of Tamerlane (1370-1405), with 20 million deaths
• Dungan revolt (1862-1877), with 16 million deaths
• Russian Civil War and Foreign Intervention (19170-1922), with 5-9 million deaths