Question

Which incident marked the beginning of first world war?

Answer 1

On September 1, 1939, just before Adolf Hitler's invasion of Poland that marked the beginning of World War II, Zygmunt Klukowski, a young Polish doctor, confided in his diary that everyone was talking about war.
This incident marked the beginning of world war.

(Hope it helps)

Answer 2

The first World War began as a local war between Austria-Hungary and Serbia in 1914. It grew into a war involving 32 countries. The Allies included Britain, France, Russia, Italy and the United States. These countries fought against the Central Powers which included Germany, Austria-Hungary, Ottoman Empire and Bulgaria.