World War I was fought from 1914 to 1918; World War II began in 1939 and ended in 1945. They are called "World" wars because of the extended areas of conflict and the very high death toll of civilians and soldiers. In World War II, the Allies – Great Britain, France, Russia and the United States – fought the Axis led by Germany, with Italy and Japan as its allies.
1. Causes of World War II
The devastation of World War I was so great that it was called The Great War or The War to End All Wars. The immediate and primary cause of World War II was the aggressive military offensive of a resurgent Germany and a fast developing Japan.
Treaty of Versailles (June 1919)
Three clauses caused great resentment among Germans: (i) Germany gave up territories to the west, north and east; (ii) Germany had to disarm and keep only a restricted armed force; (iii) Germany had to pay reparations for the military and civilian cost of the War.