A world war is a global conflict that involves all the major world powers. The term is usually reserved for two large international conflicts. World wars typically last for three years and involve hundreds of millions of people. However, they can last for a shorter duration, as can be seen in the case of the Second World War.

During the war, the Nazis made a rapid progress towards their goals. They invaded France, Belgium, and Luxembourg, and won within six weeks. The British fought back and held off the German air force in the battle of Britain, but were unable to defeat Germany alone. On 10 June 1940, Italy declared war on Britain and France. Hitler then refocused his attention towards the Soviet Union, approving a massive invasion of the USSR. In response, the United States pledged to provide increased economic assistance to Britain and the Commonwealth.

In the course of the war, the number of casualties has been estimated at more than nine million. A large number of them died on the Eastern Front before the Czarist Russian government collapsed and the Bolshevik government sued for peace. But despite the large number of casualties, the exact number of people killed in World War I will likely never be known. However, it is estimated that nine to ten million soldiers died, and between seven and eight million civilians. Among these, the United Kingdom lost over one million soldiers.

Anti-war sentiment was widespread in the United States. The country’s public opinion poll showed that ninety percent of Americans opposed the war. However, the United States’ decision to go to war with Germany triggered an international debate about the country’s role in world affairs.