This document summarizes World War I and World War II. It provides details on the start and end dates of each war, the alliances involved, and some of the underlying causes. World War I was from 1914-1918 and was between the Triple Alliance and Triple Entente. Some of the causes included nationalism, imperialism, and the alliance system. World War II was from 1939-1945 and was between the Axis powers and Allies. Causes of WWII included the consequences of WWI like the Treaty of Versailles and failure of appeasement.