January 18, 1951. Chinese and North Korean forces capture Seoul for the second time. United Nations forces recapture Seoul in March.

March 6, 1951. Ethel and Julius Rosenberg, Jewish American communists, go on trial for passing information about the atomic bomb to the Soviet Union. They are convicted and sentenced to death and later executed in 1953.

April 11, 1951. U.S. President Harry S. Truman relieves General of the Army Douglas MacArthur, a popular war hero of World War II and the commander of United Nations forces fighting in the Korean War, of command in Korea for threatening to invade China against U.S. policy.
Truman: “I fired him because he wouldn’t respect the authority of the President. I didn’t fire him because he was a dumb son of a b—, although he was, but that’s not against the law for generals. If it was, half to three-quarters of them would be in jail.”

May, 1951. People of color are removed from the election rolls in South Africa and therefore not allowed to vote.

May 9, 1951. The first thermonuclear weapon is tested on Enewetok Atoll in the Marshall Islands, by the United States.

June 14, 1951. UNIVAC, the world’s most advanced digital computing machine, is dedicated and installed in the U.S. Census Bureau in Philadelphia. UNIVAC uses vacuum tubes and occupies an entire room, 35.5 square meters of floor space. It can read 7200 digits per second.

July 5, 1951. William Shockley, John Bardeen, and Walter Brattain announce the invention of the junction transistor.

July 20, 1951. King Abdullah I of Jordan is assassinated by a Palestinian while attending Friday prayers in Jerusalem.

September 9, 1951. Chinese communist forces invade Lhasa, the capital of Tibet.

October 26, 1951. Winston Churchill is re-elected Prime Minister of the United Kingdom in a general election which sees the defeat of Clement Attlee’s Labour government after six years in power.