During the first half of the 20th century, two great international conflicts were fought: World War I and World War II. These wars had a devastating impact on the world. Millions of civilians died, and many millions of homes and property were destroyed.

World War I began in August 1914. It was caused by the emergence of two rival powers: the German Empire and the Russian Empire. It also affected colonies in Africa, Asia and the Middle East.

World War I ended in 1919 with the Treaty of Versailles, which forced Germany to recognize its responsibility for the war. It also forced Germany to give up 13 percent of its European territory. The treaty was a bitter pill to swallow. It led to the rise of Adolf Hitler in Germany and the Soviet Union’s rise as a rival superpower.

World War II lasted from 1939 to 1945. It was the deadliest international conflict in history. The conflict involved all of the world’s major powers: the United States, Germany, Japan, Italy, France, and Russia. The United States and Britain, which had been allied during World War I, joined the fight against Germany.

After the armistice with Russia, the Germans began to build up their strength on the Western Front. They also invaded Belgium and Luxembourg. The Germans’ strength increased rapidly, but they were unable to make headway against the Allied armies.

Germany also attacked the Soviet Union. In December 1940, Hitler approved a large-scale invasion of the Soviet Union. Thousands of Russian civilians died of gas poisoning.