World War I, also known as the First World War, began on 28 July 1914 and ended on 11 November 1918. The conflict affected many countries and caused millions of deaths. The war is considered to be one of the worst conflicts in history. This is because so many nations were involved and the war was very bloody. Many people were killed and hundreds of millions were displaced.

The conflict was also characterized by the escalation of technology. The use of guns, airplanes, and other weapons made war more deadly than ever before. It also resulted in the collapse of four great empires. The world also underwent a profound social and economic upheaval. Ultimately, this war would pave the way for World War II. In addition, it would lead to the Bolshevik Revolution in Russia and destabilize European society.

The war was the most widespread in history. It involved more than 30 countries and lasted six bloody years. It killed 60 to 80 million people, including more than a million Jews. The war also destroyed more land than any previous war. In addition, there were at least nine to ten million casualties on each side. The United States, France, Japan, Italy, Canada, the Soviet Union, and other nations lost more than a million soldiers.

In 1940, the Soviet Union invaded Poland, which was under attack from both sides. The Allies won the war and established the League of Nations to promote international cooperation. The Soviet Union emerged as a rival superpower. World War II also brought Western democracies into conflict with the Soviet Union. Two nuclear-armed blocs probed each other for weaknesses. In addition, the European economy collapsed following the war.