1940s

The 1940s decade ran from 1940 to 1949. The Forties saw the expansion of the Second World War and its end in 1945. Thereafter a Cold War developed between the Soviet Union and the Western Allies in Europe and the United States.

Wars and Conflicts

Germany invades Denmark, Norway, Benelux, and the French Third Republic from 1940 to 1941
Germany faces the United Kingdom in the Battle of Britain (1940). It was the first major campaign to be fought entirely by air forces, and was the largest and most sustained aerial bombing campaign up until that date.
Germany attacks the Soviet Union (June 22, 1941)
The United States enter World War II after the attack on Pearl Harbor on December 7, 1941. It would face the Empire of Japan in the Pacific War.
Germany and Japan suffer defeats at Stalingrad, El Alamein, and Midway in 1942 and 1943
Normandy Landings. The forces of the Western Allies land on the beaches of Normandy in Northern France (June 6, 1944)
Yalta Conference, wartime meeting from 4 February 1945 to 11 February 1945 among the heads of government of the United States, the United Kingdom, and the Soviet Union—President Franklin D. Roosevelt, Prime Minister Winston Churchill, and Premier Joseph Stalin, respectively—for the purpose of discussing Europe's postwar reorganization, intended to discuss the re-establishment of the nations of war-torn Europe.
Germany surrenders (May 7–8, 1945)
Atomic bombings of Hiroshima and Nagasaki (August 6 and August 9, 1945); Surrender of Japan on August 15
World War II officially ends on September 2, 1945

Establishment of the United Nations Charter (June 26, 1945) effective (October 24, 1945)
Establishment of the defense alliance NATO April 4, 1949.

1944 - Iceland declares independence from Denmark.
1945 - Indonesia declares independence from the Netherlands (effective in 1949 after a bitter armed and diplomatic struggle).
1946 - The French Mandate for Syria and the Lebanon dissolves to the independent states of Syria and Lebanon. The French settlers are forced to evacuate the French colony in Syria.
1947 - Partitioning of the British Raj into a secular Union of India and a Muslim Dominion of Pakistan. British rule in Burma ends in 1948.
1948 - Establishment of the State of Israel.

The Electronic Numerical Integrator and Computer (ENIAC) is constructed as the first digital electronic computer.
Construction of the Colossus computer which was used by British codebreakers to read encrypted German messages during World War II.
The first test of technology for an atomic weapon is made (Trinity test) as part of the Manhattan Project.
The development of the Radar.
The development of the Ballistic missiles
The development of the Jet aircraft

Physics: the development of the quantum theory and nuclear physics.
Mathematics: the development of the Game Theory and Cryptography.
Thor Heyerdahl's Kon-Tiki crossed the Pacific Ocean proving the practical possibility that people from South America could have settled Polynesia in pre-Columbian times.
Willard Libby developed the radiocarbon dating - a process which revolutionized archaeology.
The development of Modern evolutionary synthesis.

Chancellor Adolf Hitler (Germany)
President Franklin D. Roosevelt (United States)
General Secretary Joseph Stalin (Soviet Union)
Emperor Hirohito (Japan)
President Charles de Gaulle (France)
Prime Minister Winston Churchill (United Kingdom)
Prime Minister Benito Mussolini (Italy)
Prime Minister David Ben Gurion (Israel)
Prime Minister Clement Attlee (United Kingdom)
Prime Minister John Curtin (Australia)
Head of state Francisco Franco (Spain)
President İsmet İnönü (Turkey)
Governor-General Muhammad Ali Jinnah (Pakistan)
Chairman Chiang Kai-shek (Nationalist China) (Taiwan)
Prime Minister William Lyon Mackenzie King (Canada)
Prime Minister and President Hồ Chí Minh (Democratic Republic of Vietnam) (North Vietnam)
Prime Minister Liaquat Ali Khan(Pakistan)
Prime-Minister Pandit Jawaharlal Nehru (India)
President Juan Perón (Argentina)
General Aung San (Burma)
President Harry S. Truman (United States)
President Getúlio Vargas (Brazil)
Chairman Mao Zedong (China)
President Romulo Betancourt (Venezuela)