At the Munich Conference Hitler promised to not invade anymore regions if he could keep Czechoslovakia. Britain and France agreed so a war wouldn´t be started. However, in September of 1939 German troops invaded Poland.
December 7, 1942 Japanese planes attacked the Naval Base of Pearl Harbor in Hawaii. This killed thousands of Americans and became a turning point in the war.
While the US had tried to keep a sense of neutrality in the war while still aiding the countries, the attack of Pearl Harbor forced us to jump into war. December 8, 1941 President Roosevelt declared war on Japan. This allied the US to Britain and France.
D-Day was a series of attacks on the shore of Normandy by American, Canadian, and British troops. This helped gain control over those parts of Russia. This is also known as one of the greatest attacks.
After having the atomic bomb under cover calling it the ¨Manhattan Project¨, the US finally decided to drop it in the Japanese city of Hiroshima. The bomb caused mass destruction and a couple weeks later they dropped a second one on Nagaski. Once again there was another turning point in the war.
While Hitler had been torturing and killing Jews throughout the whole war, the rest of the world wasn´t fully aware until the end. After the liberating armies broke into the concentration camps they discovered what had been going on in Germany. The world was devastated.