World Wars - Definition and Overview

There have been two world wars, now more commonly known as World War I or First World War (from 1914 to 1918) and World War II or Second World War (from 1939 to 1945). At the time of the first world war, it was widely believed that never again would there be a world war like the first; consequently it was known at that time and in the years that followed as 'The Great War'.

The Great War later become known as World War One, when World War II began in 1939, following Germany's invasion of Poland led by German leader Adolf Hitler.