Causes of US Involvement in World War II
Following World War I, the United States adopted an isolationist stance. Starting in 1935,
Congress even passed various neutrality acts to enforce the will against foreign
entanglement. But by December of 1941, President Roosevelt’s formal declaration of war
made this legislation irrelevant.
Although America attempted isolationism, European and Asian affairs brought global
tension that eventually hit the country’s traditional allies. An aim of World War I had
been “to make the world safe for democracy”, but democracy in the 1930s was
increasingly endangered. The roots of World War II lay in the totalitarian leaders of Asia
and Europe and their agendas for expansion.
Totalitarianism emerged in the Soviet Union, Italy, Spain, and Germany. The fascist
leaders had expansionist goals and soon crushed neighboring societies. Italy invaded
Ethiopia and established Italian East Africa. Meanwhile, Japan invaded Manchuria,
seized Chinese land, and occupied French possessions in Southeast Asia.
In 1938 Europe, the war officially began when Germany’s Adolf Hitler invaded Austria
and took Czechoslovakia’s Sudetenland, which was home to 3.5 million ethnic Germans.
Hitler claimed he was only “restoring rightful boundaries”, since Germany had lost
territory in World War I. But Hitler had ideas of widespread domination. In 1939 he and
Mussolini created the Rome-Berlin Axis alliance, a military agreement designed to last
ten years. Japan entered the pact later that year. Hitler had the confidence to invade
Poland in 1939. Poland’s allies, England and France, therefore declared war on Germany.
America’s traditional allies were at war.
Initially, President Franklin Roosevelt limited his aid to arms sales, which were restricted
in a neutrality act. But Hitler’s invasions continued. He took Denmark, Norway, and
Holland, and the Belgian king surrendered his army shortly thereafter. And in June of
1940, France succumbed to Nazi forces. The Axis alliance now dominated Europe from
the North Cape of Africa to the Pyrenees. Great Britain’s Winston Churchill vowed to
continue the battle for democracy.
Churchill soon needed military aid, and Roosevelt declared that the United States must
become “the great arsenal of democracy”. By 1941, he officially ended the country’s
isolationist stance by passing the Lend Lease Act, which lifted restrictions on supporting
foreign troops with defense gear; the Act first appropriated $7 billion to lend or lease
supplies to any countries the president designated. President Roosevelt also started to call
US National Guard members to war training.
Next, the Americans built a base in Greenland. Then, stationed aboard warships near
Newfoundland, Roosevelt and Churchill issued the Atlantic Charter in June of 1941.
Although the US had not officially entered the war, the Atlantic Charter presented the
two countries’ goals for a war against fascism. It included their disinterest in acquiring
new territories through the war. Shortly thereafter, the US became involved in the years-
long Battle of the Atlantic.
The United States officially entered World War II in December of 1941. Japanese
military leaders, led by Admiral Isoroku Yamamoto, attacked a US naval base in Pearl
Harbor, Hawaii. The Japanese aimed to destroy the US fleet docked in the Pacific, thus
leaving the Japanese free to pursue oil mines in the region. A series of aerial attacks by
361 airplanes succeeded in compromising eight important warships. The air attacks also
killed more than 2,300 people. The following day, President Roosevelt asked Congress
for a declaration of war against Japan. Congress obliged. By the time of this official
declaration, there were battles to fight on many fronts, but “Remember Pearl Harbor!”
became a rally cry for the war.