Final answer:
Hitler's confidence in invading Russia was bolstered by the rapid capture of France, which fell swiftly to the Nazi's blitzkrieg tactics, leading to a significant territorial advantage in Europe for the Nazis.
Step-by-step explanation:
Hitler was confident about invading Russia because he had recently captured France. After quickly overcoming Denmark and Norway, the Nazi military executed a blitzkrieg into Western Europe, avoiding the fortified French-German border by moving through the Netherlands and Belgium. This strategy led to the rapid fall of France, with Hitler eventually posing in front of the Eiffel Tower. The swift fall of France, along with Poland, and territories in the Balkans and North Africa, gave the Nazis control over significant parts of Europe, promising enough resources to attempt the invasion of the Soviet Union in 1941.