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Thailand declares war on the United States and United Kingdom. -
President Franklin D. Roosevelt signs an executive order directing the internment of Japanese Americans and the seizure of their property. -
The Casablanca Conference, where Franklin D. Roosevelt becomes the first President of the United States to travel by airplane while in office -
Winston Churchill addresses a joint session of the U.S. Congress. -
Operation Overlord, commonly known as D-Day, commences with the landing of 155,000 Allied troops on the beaches of Normandy in France. The Allied soldiers quickly break through the Atlantic Wall and push inland, in the largest amphibious military operation in history. This operation helps liberate France from Germany and also weakens the Nazi hold on Europe. -
American and Filipino troops (with Filipino guerrillas) begin the Battle of Leyte in the Philippines. -
Naval Battle of Leyte Gulf in the Philippines – In the largest naval battle in history by most criteria and the last naval battle in history between battleships, -
Franklin D. Roosevelt wins reelection over Republican challenger Thomas E. Dewey, becoming the only U.S. president elected to a fourth term. -
Franklin D. Roosevelt is inaugurated to an unprecedented fourth term as President of the United States. No president before, or since, reaches a third term in office. Harry S. Truman is sworn in as Vice President of the United States. -
President Franklin D. Roosevelt dies suddenly at Warm Springs, Georgia; Vice President Harry S. Truman becomes the 33rd President. -
Atomic bombing of Hiroshima: The United States drops an atomic bomb (nicknamed "Little Boy") on Hiroshima, Japan, at 8:15 a.m. (local time). This sent shockwaves throughout the world as the first atomic bomb used on civilians. -
Emperor Hirohito announces Japan's surrender on the radio. The United States calls this day V-J Day (Victory over Japan). This ends the period of Japanese expansionism and begins the period of Occupied Japan. -
The United Mine Workers rejoins the American Federation of Labor. -
The Central Intelligence Group is established -
Jackie Robinson becomes the first official African American to play Major League Baseball (Since the 1880s) -
In an effort to fight the spread of Communism, President Harry S. Truman signs an Act of Congress that implements the Truman Doctrine. The Act grants $400 million in military and economic aid to Turkey and Greece. -
Democratic incumbent Harry S. Truman defeats Republican Thomas E. Dewey and 'Dixiecrat' Strom Thurmond. -
The first Volkswagen Beetle to arrive in the United States, a 1948 model, is brought to New York City by Dutch businessman Ben Pon. -
President Harry S. Truman begins his full term. Alben W. Barkley is sworn in as Vice President of the United States. -
Troops from the People's Republic of China move into North Korea and launch a massive counterattack against South Korean and American forces at Chosin, dashing any hopes for a quick end to the conflict. -
Republican candidate Dwight D. Eisenhower defeats Democratic Governor of Illinois Adlai Stevenson -
President Harry S. Truman announces the United States has developed a hydrogen bomb. -
Dwight D. Eisenhower is sworn in as the 34th President of the United States, and Richard Nixon is sworn in as Vice President of the United States. -
U.S. President Dwight D. Eisenhower formally approves the top secret document of the United States National Security Council NSC 162/2, which states that the United States' arsenal of nuclear weapons must be maintained and expanded to counter the communist threat.