Question

What led England and France to declare war on Germany, marking the start of World War II?

Hitler rounded up European Jews and put them in camps.
B
Germany invaded the Soviet Union.
After gaining the Sudetenland through an agreement, Germany then took the rest of Czechoslovakia.
Germany invaded Poland, a country Britain and France had promised to protect.
Germany invaded Austria, the place of Hitler's birth.

Answer 1

England and France declared war on Germany after the invasion of Poland, violating a promise to protect Poland.

Step-by-step explanation:

The declaration of war by England and France on Germany, marking the start of World War II, was primarily triggered by Germany's invasion of Poland. This act violated the promise made by Britain and France to protect Poland. On September 1, 1939, Germany launched a military attack on Poland, prompting Britain and France to fulfill their commitment and declare war on Germany.

While other actions by Germany, such as the invasion of Austria and the occupation of Czechoslovakia's Sudetenland, were concerning to the Allies, it was the invasion of Poland that ultimately led to the war.

It's important to note that the rounding up of European Jews and putting them in camps, which is mentioned in the question, was a horrific aspect of the Holocaust, but it was not the direct cause for England and France declaring war on Germany.

Learn more about England and France's declaration of war on Germany at the start of World War II