Watch World War II: Cause and Effect (2015) : Full Movie Online Free The conflict that engulfed the world between 1914 and 1918 left an indelible mark on the 20th century and shaped the world in which we live today. Learn about the tumultuous events that led to World War I, the complex alliances, the Russian Revolution and the rise of communism, and much more. The complete story of the first modern war.