Who did the United States fight in World War II?

Why this is the answer

The official answer names three countries, Japan, Germany and Italy, and the safest habit is to say all three. Together they were the Axis powers. The alliance took shape in Europe first: the war began in 1939 when Germany invaded Poland, France and Great Britain answered by declaring war on Germany, and Germany was already allied with Italy and Japan. For about two years the United States stayed out. That ended on December 7, 1941, when Japan launched a surprise attack on U.S. naval bases at Pearl Harbor, Hawaii. The next day Franklin Roosevelt, acting as commander in chief, announced that the country would enter the war, and later that day Congress voted to declare it, a power the Constitution gives to the federal government. Notice that the declaration Roosevelt signed that day named Japan. Germany and Italy, Japan’s Axis partners, then declared war on the United States, and that is how the country came to fight on opposite sides of the globe at once, in Europe, Africa, Asia and the Pacific. It did not fight alone. The United States joined France, Great Britain and the Soviet Union as the Allied powers, led the D-Day invasion of France in 1944, and saw Europe freed from German control by May 1945. Japan held out longer, and the war ended only with its surrender that September. Two mistakes are easy to make. One is naming only Japan, because Pearl Harbor is the attack that brought the United States into the war, which leaves the answer incomplete. The other is adding the Soviet Union, or Russia, because it later became the great rival of the Cold War; in World War II it fought on the same side as the United States. To keep the trio straight, think of the regimes the Allies faced: the German Nazis, the Italian Fascists and Japan’s military empire. Then picture a map with one enemy in the Pacific and two in Europe, all three bound by the same alliance.