Why did world war ll start?

World War II—which broke out two decades later and would prove even more devastating. Rising to power in an economically and politically unstable Germany, Adolf Hitler, leader of the Nazi Party, rearmed the nation and signed strategic treaties with Italy and Japan to further his ambitions of world domination. Hitler’s invasion of Poland in September 1939 drove Great Britain and France to declare war on Germany, marking the beginning of World War II. Over the next six years, the conflict would take more lives and destroy more land and property around the globe than any previous war. Among the estimated 45-60 million people killed were 6 million Jews murdered in Nazi concentration camps as part of Hitler’s diabolical “Final Solution,” now known as the Holocaust.

Many causes, but the most major ones include: The impact of the treaty of Versailles following WWI, worldwide economic depression, the rise of militarism in Germany and Japan. Germany's invasion of Poland in 1939 lead to the outbreak of WWII.

The Byzantine Empire, known also as the Eastern Roman Empire, had control over a large portion of the former Roman Emperor, Including Constantinople, later known as Tsarigrad, nowadays known as Istanbul.