World War II was chock-a-block full of atrocities. Many of them, frankly, nastier than the sneak attack on Pearl Harbor.
December 13, 1937 - Rape of Nanking
Army officers competed against each other to see who could kill the most Chinese first. Thousands of women were gang-raped to death. All totaled, over 300,000 Chinese were brutally murdered during the first few weeks of the Japanese occupation of Nanking.
November 9, 1938 - Kristallnacht
September 29, 1941 - Babi Yar
February 13, 1945 - Dresden
RAF commander "Bomber" Harris set his sights on Dresden. One of the most culturally significant cities in Europe with no military significance, Dresden had become a gathering place of refugees fleeing the advancing Russian army. Ostensibly attacking Dresden's communications infrastructure, the raid mostly avoided bridges and rail lines and instead targeted the civilian population of the city center with almost 8 million pounds of mostly incendiary explosives. The resulting firestorm burned for days and killed some 25,000 non-combatants and zero combatants.
August 9, 1945 - Nagasaki