March 1: Puerto Rican freedom fighters/terrorists led by Lolita Lebron open fire in the U.S. House of Representatives. Five Representatives were wounded. Their attack was a violent protest against the United States' "military occupation" of their country. The attackers were released from prison in 1979.
March 1: Fukuryu Maru Incident. The United States conducts the largest ever test of nuclear weapons at Bikini Atoll with the open-air detonation of hydrogen or fusion weapon called Bravo Shot. Bikini islanders displaced and their island poisoned with radioactivity. Fallout from the blast lands on the crew of the Japanese tunaboat Fukuryi Maru V or Lucky Dragon 5 80 nautical miles away. One dies and others are sickened by radiation poisoning.
March 4: Japanese parliament approves budget for nuclear power development.
June 2: Report on producing H-bombs presented to the British Chiefs of Staff by the Working Party on the Operational Use of Atomic Weapons (OAW). The British Chiefs eventually recommend producing a British H-bomb a goal to be achieved by 1958.
June 7: British mathematician, WWII code-breaker and marathon athlete Alan Turing either commits suicide or is murdered after consuming an apple laced with cyanide. British secret services believed Turing was a security threat because he was gay.
June 17: Vietnamese "Emperor" Bao Dai names Ngô Đình Diệm as premier of South Vietnam.
June 17: U.S. supported invasion of democratic Guatemala from Honduras by 150 wingnut exiles and a professional disinformation operation.
June 27: Democratically elected Guatemalan President Jacobo Arbenz is forced to resign.