After World War I, America entered into a phase of isolationist foreign policy. By 1935, Congress was actually passing a number of neutrality acts designed to formally enforce the idea of staying out of foreign involvements. However, this ended in December of 1941, as President Roosevelt asked Congress for a formal declaration of war. They approved, marking the entry of America into the hostilities already raging around the world.
Even though the United States entertained a relatively brief experiment with isolationism, matters on other continents raised global tensions and rivalries to a boil. These matters and conflicts quickly succumbed quite a few allies on both sides of the conflict. One idea popular in World War I was trying to create a world that was going to be a safe place for democratic nations. However, World War II started up in large part because totalitarian leaders on the continents of both Europe and Asia had expansionist ambitions.
The grasp of totalitarianism reached a fervent pitch in places like Germany and the Soviet Union, as well as Italy and Spain. Italy conducted an invasion of Ethiopia before forming Italian East Africa. Likewise, Japan decided to invade Manchuria and French territories in the region.
The official start of World War II in Europe was when Germany invaded places like Austria and Czechoslovakia. Hitler was particularly interested in Sudetenland and its millions of ethnic Germans living there, claiming that he was just restoring the rightful borders of Germany the country had lost during the previous world war.
This was only the start though, as he and Italian leader Mussolini formed an Axis alliance. Japan entered this military pact later the same year of 1939. This gave Hitler enough confidence to invade Poland, whose allies of France and England were now drawn into war.
The United States did not sit idly by, but neutrality acts restricted the president to just some arms sales. During this time, Nazi Germany rolled through Holland, Norway, and Denmark. The king of Belgium simply surrendered. By the middle of 1940, France fell. England alone remained as a free democracy.
Winston Churchill of Britain pledged to fight the good fight, but he was going to need help. The isolationist period of America started ending in 1941 with the Lend-Lease Act, lifting the previous restrictions, and freeing up billions in aide to chosen countries. The National Guard was also called up for war training.
The United States constructed a base on the island of Greenland, but it was in the Pacific that isolationism ended fully. In December of 1941, a Japanese strike force surprise-attacked the US Navy base located at Pearl Harbor in the state of Hawaii.
It was 361 Japanese airplanes that damaged or sunk eight crucial warships, killing over 2,300 people. Japan’s hope was to free the Pacific of an American presence so they could freely exploit oil and petroleum resources throughout the region. It was just the next day that the President requested a formal declaration of war against Japan. It was issued, and formal hostilities with Germany were also declared almost immediately.