Which event is generally considered to be the first belligerent act of world war ii?

Germany's attack on Poland is generally considered to be the first belligerent act of Word War II.

Explanation:

The event that is considered as the first belligerent act of World War II was the invasion of Poland by Nazi Germany under the command of Adolf Hitler. During this event, many civilians lost their lives as Poland was not completely prepared for this attack.

After the occurrence of this event, Britain and France declared war against Germany as Hitler refused to stop his invasion of Poland. After this, many countries started becoming part of the War in one way or the other and the consequences were deadly.