During World War I, millions of people were killed and millions of homes were destroyed. The war resulted in the collapse of the Czarist Empire and the formation of the League of Nations. It also created a new superpower, the United States, which fought against Germany, Japan, and Russia.
World War II lasted from 1941 to 1945 and was even more devastating than World War I. The United States, Great Britain, and Japan were all involved, along with many other countries and non-European powers. It was the deadliest international conflict in history, killing 50 to 55 million civilians. It was fought mostly on the sea, but the United States also engaged in a large number of land battles.
The war started with the German invasion of Poland. The Allies were France and Great Britain. The Allies were able to hold off the German offensive until reinforcements from the United States arrived.
The war was not immediately declared. The United States joined the fight against Germany in December 1941. They were later joined by Japan and China. The Allies fought on the Eastern Front and the Western Front.
In 1939, Germany invaded Poland. The German High Command sued for an armistice, but the Departments of State and Defense were skeptical that the Soviet Union would deliberately target Poland. The Russian government responded by sending troops to Poland from the east.
The war ended when Germany agreed to a series of peace treaties. The Treaty of Versailles was signed in 1919. It acknowledged Germany’s responsibility for the war. The treaty recognized that the nations of the world were divided into two camps – the Allies and the Central Powers.