What was the most important thing that happened in war two

1. Hitler invaded Poland in September 1939

2. Anti-semitism

Explanation:

1. France and Britain declared a war. After the war, Germany started attacking France. which then France fell apart in 1940. Which meant Germany took the rest of Europe and north America.

2. Since the Nazi were gaining popularity they put signs of Jews are not wanted here. Which meant if they find one, they will be killed. Even the Nazi would destroy every store the Jews owned.