European leaders of England and France were slow to stop the advances of Hitler in Mussolini because

British and French leaders were slow to stop the advances of the Axis Powers in World War II as they thought that they could appease them into ceasing their campaign for expansion.

This police, known as "appeasement", ultimately was a failure as the Allied leaders miscalculated the extent to which Hitler & Co. had eyes on an Empire that would stretch the entirety of Europe.

In the end, the leader in England advocating appeasement would be replaced and France would be overrun by the Germans.