Japan bombed the Pearl Harbor naval base in Hawaii on Dec. 7, 1941, and declared war on the United States. The next day, President Franklin D. Roosevelt appeared before a joint session of Congress, asked for a declaration of war against Japan and described it as, “a date which will live in infamy.” Congress approved the declaration of war, and within days, Germany and Italy had declared war on the United States, which was now embroiled in World War II.

[Pictured: President Franklin D. Roosevelt on Dec. 8, 1941, as he asks Congress to declare a state of war against Japan.]

President Roosevelt authorizes internment camps for Japanese Americans living on the West Coast. Approximately 100,000 people were forced to leave their homes for camps in Arkansas, Colorado, and Utah. The policy is now considered one of the most shameful in American history.

[Pictured: Exclusion Order posted in San Francisco on April 11, 1942.]

President Franklin D. Roosevelt, Soviet Premier Joseph Stalin, and British Prime Minister Winston Churchill first met in Tehran, Iran, from late November until Dec. 1. The men agreed on the Allied invasion of Europe, Premier Stalin promised to join the fight against Japan, and they discussed plans for after the war. The leaders came to be called “The Big Three.”

[Pictured: Joseph Stalin, Franklin D. Roosevelt, and Winston Churchill on the veranda of the Soviet Legation in Tehran, during the first "Big Three" conference.]

The G.I. Bill of Rights was meant to help World War II service members rejoin society. Formally the Servicemen’s Readjustment Act of 1944, the bill offered low-cost mortgages, business loans, tuition to attend college, and an unemployment benefit of $20 a week. Congressional opposition to the unemployment benefit nearly killed the bill. Millions attended colleges and universities, bought houses, and relatively few collected the unemployment check.

[Pictured: The USS Washington arrives in the New York Harbor on June 11, 1945.]

Harry S. Truman, who was thrust into the presidency when President Franklin D. Roosevelt died in April, approved the first and only use of atomic weapons, authorizing dropping atomic bombs on Hiroshima on Aug. 6 and on Nagasaki on Aug. 9. Japan surrendered on Aug. 15, and President Truman said he never regretted his decision. An estimated 225,000 people were killed, crushed in buildings, or from burns or radiation poisoning.

[Pictured: President Truman announces Japan's surrender at the White House, on Aug. 14, 1945.]

The 1946 midterm elections gave Republicans the majority in both the House of Representatives and the Senate for the first time since 1928. Republicans added 56 seats in the House and 13 in the Senate, seemingly presaging a difficult election for President Harry Truman in his own right in two years.

[Pictured: Chair of the Democratic National Committee, American politician, and attorney James Howard McGrath during the 1948 Democratic Convention on July 12 in Philadelphia.]

Secretary of State George Marshall proposed the United States help Europe rebuild its economy after World War II. Congress passed the Economic Cooperation Act of 1948, which became known as the Marshall Plan, and set aside $13.3 billion for European recovery over four years. The United States benefited too, creating democracies in Europe and partners in trade.

In the same year, President Harry Truman gave $400 million in aid to Turkey and Greece to fend off Communism, marking the start of the Cold War.

[Pictured: Secretary of State George Marshall as he testifies before the Senate Foreign Relations Committee, Jan. 9, 1948.]

President Harry Truman won his own term despite widespread expectations that he would lose to New York Gov. Thomas Dewey. “Dewey defeats Truman,” read the famously mistaken front page of the Chicago Daily Tribune. Truman had campaigned against a “do-nothing Congress” that had not passed his legislative proposals and had won support from unions with his veto of the Taft-Hartley bill that restricted their power. Congress overrode the veto.

[Pictured: President Harry S. Truman laughing as he holds an early edition of the Chicago Daily Tribune for Nov. 4th, 1948.]

NATO, or the North Atlantic Treaty Organization, was signed in 1949 to counter the Soviet Union, with the 12 founding members agreeing to protect one another in a collective defense. An attack against one member of the treaty is considered an attack on all. The treaty, which President Harry Truman helped to negotiate, was the first peacetime agreement that the United States joined in Europe.

North Korea invaded South Korea with the backing of the Soviet Union, after the secretary of state omitted South Korea when describing the American “defensive perimeter.” The North Koreans did not expect the United States to respond, but it went to the United Nations Security Council, and sent American troops. A cease-fire was reached in 1953, but not before millions of casualties. President Harry Truman acted without Congressional approval, expanding presidential power in the ability to go to war.

[Pictured: Brigadier Gen. Courtney Whitney, Gen. Douglas MacArthur, and Maj. Gen. Edward Almond (at right, pointing), in Korea, observe the shelling of Incheon from the USS Mount McKinley (AGC-7), on Sept. 15, 1950.]