Attack on Pearl Harbor

Japan launched a surprise attack on the United States Pacific fleet at Pearl Harbor, Hawaii, severely damaging the military installations there. 

In response to the attack, the United States declared war on Japan. A few days later, Germany, which was Japan's military ally, declared war on the United States. The US Congress then declared war on Germany. 

Japan also attacked and occupied Guam, Wake, the Philippines, the Dutch East Indies, Hong Kong, Malaya, Singapore, and Burma.