Question

When did world war 2 start

Answer 1

People argue about the official date, but most historians agree that is was on September 1st, 1939 (when Germany invaded Poland).

Answer 2

World War 2 started on Friday, September 1, 1939, when Hitler and his Nazi forces invaded Poland. Two days later, Britain and France declared war on Germany, on Sunday, September 3, 1939, officially starting World War 2.

On Sunday, September 17, 1939, Soviet Forces invaded Poland from the eastern side. 

Hope this helps!