World War II had several significant themes: 1. The policy of appeasement failed to prevent war as Hitler continued his aggression and took over more territory. 2. New mobile warfare tactics using planes, tanks, and radios allowed for quick lightning attacks and the invasion of France in 1940. 3. Civilians became targets of air attacks as residential areas near factories were bombed, causing many deaths in places like London, Coventry, Dresden, and the firebombing of Tokyo. Over 6 million Jews were killed in the Holocaust.