April 23: US President Harry S. Truman gives a tongue-lashing to Soviet Foreign Minister Vyacheslav Molotov indicating that he was determined to take a "tougher" stance with the Soviets than his predecessor had.
August 6: Truman gives permission for the world's first military use of an atomic weapon against the Japanese city of Hiroshima in an attempt to bring the only remaining theatre of war from the Second World War in the Pacific to a swift closure.
August 8: The USSR honors its agreement to declare war on Japan within three months of the victory in Europe, and invades Manchuria. In accordance with the Yalta Conference agreements, the Soviet Union also invades Japanese Sakhalin and the Kuril Islands.
August 9: US President Truman gives permission for the world's second and last military use of an atomic weapon against the Japanese city of Nagasaki in order to try to secure a swift Japanese unconditional surrender in the end of the Second World War.
September 5: Igor Gouzenko, a clerk working in the Soviet embassy in Ottawa, Canada, defects and provides proof to the Royal Canadian Mounted Police of a Soviet spy ring operating in Canada and other western countries. The Gouzenko affair helps change perceptions of the Soviet Union from an ally to a foe.
July 11: The US announces new occupation policies in Germany. The occupation directive JCS 1067, whose economic section had prohibited "steps looking toward the economic rehabilitation of Germany [or] designed to maintain or strengthen the German economy", is replaced by the new US occupation directive JCS 1779 which instead notes that "An orderly, prosperous Europe requires the economic contributions of a stable and productive Germany."
August 14: India and Pakistan gain independence from the United Kingdom.
September: The Soviet Union forms the Communist Information Bureau (COMINFORM) with which it dictates the actions of leaders and communist parties across its spheres of influence.
November 14: The United Nations passes a resolution calling for the withdrawal of foreign soldiers from Korea, free elections in each of the two administrations, and the creation of a UN commission dedicated to the unification of the peninsula.
June 21: In Germany, the Bizone and the French zone launch a common currency, the Deutsche Mark.
June 24: Soviet PremierJoseph Stalin orders the blockade of all land routes from West Germany to Berlin, in an attempt to starve out the French, British, and American forces from the city. In response, the three Western powers launch the Berlin Airlift to supply the citizens of Berlin by air.
June 28: The Soviet Union expels Yugoslavia from the Communist Information Bureau (COMINFORM) for the latter's position on the Greek civil war.
June 28 to May 11, 1949: The Berlin Airlift defeats Russia's attempt to starve West Berlin.
November 20: The American consul and his staff in Mukden, China, are made virtual hostages by communist forces in China. The crisis did not end until a year later, by which time U.S. relations with the new communist government in China had been seriously damaged.
October 16: Nikos Zachariadis, leader of the Communist Party of Greece, declares an end to the armed uprising. The declaration brings to a close the Greek Civil War, and the first successful containment of communism.
June 25: North Korea invades South Korea. The Soviet Union cannot veto, as it is boycotting the Security Council over the admission of People's Republic of China. Eventually, the number of countries operating under the UN aegis increases to 16: Australia, Belgium, Canada, Colombia, Ethiopia, France, Greece, Luxembourg, the Netherlands, New Zealand, the Philippines, South Africa, Thailand, Turkey, the United Kingdom, and the United States.
July 4: United Nations forces engage North Korean forces for the first time, in Osan. They fail to halt the North Korean advance, and fall southwards, towards what would become the Pusan Perimeter.
September 30: United Nations forces land atInchon. Defeating the North Korean forces, they press inland and re-capture Seoul.
October 2: United Nations forces cross the 38th parallel, into North Korea.
October 5: Forces from the People's Republic of China mobilize along the Yalu River.
October 22: Pyongyang, the capital of North Korea, falls to United Nations forces.
October 22: China intervenes in Korea with 300,000 soldiers, catching the United Nations by surprise. However, they withdraw after initial engagements.
November 15: United Nations forces approach the Yalu River. In response, China intervenes in Korea again, but with a 500,000 strong army. This offensive forces the United Nations back towards South Korea.
September 1: Australia, New Zealand, and the United States sign the ANZUS Treaty. This compels the three countries to cooperate on matters of defense and security in the Pacific.
October 10: President Harry S. Truman signs the Mutual Security Act, announcing to the world, and its communist powers in particular, that the U.S. was prepared to provide military aid to "free peoples."
November 14: President Harry Truman asks Congress for U.S. military and economic aid for the communist nation of Yugoslavia.
December 12: The International Authority for the Ruhr lifted part of the remaining restrictions on German industrial production and on production capacity.
April 28: the Treaty of San Francisco, signed by Japan on September 8, 1951, comes into effect, and Japan signs the Treaty of Taipei, formally ending its period of occupation and isolation, and becoming a sovereign state.
January 21: The United States launches the world's first nuclear submarine, USS Nautilus. The nuclear submarine would become the ultimate nuclear deterrent.
May 7: The Viet Minh defeat the French at Dien Bien Phu. France withdraws from Indochina, leaving four independent states: Cambodia, Laos, and what became North Vietnam and South Vietnam. The Geneva Accords calls for free elections to unite Vietnam, but none of the major Western powers wish this to occur in the likely case that the Viet Minh (nationalist Communists) would win.
May: The Huk revolt in the Philippines is defeated.
June 2: Senator Joseph McCarthy claims that communists have infiltrated the CIA and the atomic weapons industry.
June 18: The elected leftist Guatemalan government is overthrown in a CIA-backed coup. An unstable rightist regime installs itself. Opposition leads to a guerrilla war with Marxist rebels in which major human rights abuses are committed on all sides. Nevertheless, the regime survives until the end of the Cold War.
October 23: Hungarian Revolution of 1956: Hungarians revolt against the Soviet dominated government. They are crushed by the Soviet military, which reinstates a Communist government.
October 29: Suez Crisis: France, Israel, and the United Kingdom attack Egypt with the goal of removing Nasser from power. International diplomatic pressures force the attackers to withdraw. Canadian Lester B. Pearson encourages the United Nations to send a Peacekeeping force, the first of its kind, to the disputed territory. Lester B. Pearson wins a Nobel Peace Prize for his actions, and soon after becomes Canadian Prime Minister.
January 5: The Eisenhower doctrine commits the US to defending Iran, Pakistan, and Afghanistan from Communist influence.
January 22: Israeli forces withdraw from the Sinai, which they had occupied the previous year.
May 2: Senator Joseph McCarthy succumbs to illness exacerbated by alcoholism and dies.
October 1: The Strategic Air Command initiates 24/7 nuclear alert (continuous until termination in 1991) in anticipation of a Soviet ICBM surprise attack capability.
October 4: Sputnik satellite launched. The same day the Avro Arrow is revealed.
November 3: Sputnik 2 was launched, with the first living being on board, Laika.
November 7: The final report from a special committee called by President Dwight D. Eisenhower to review the nation's defense readiness indicates that the United States is falling far behind the Soviets in missile capabilities, and urges a vigorous campaign to build fallout shelters to protect American citizens.
November 15: Soviet leader Nikita Khrushchev claims that the Soviet Union has missile superiority over the United States and challenges America to a missile "shooting match" to prove his assertion.
June: A C-118 transport, hauling freight from Turkey to Iran, is shot down. The nine crew members are released by the Russians little more than a week later. 
July 14: A coup in Iraq, the 14 July Revolution, removes the pro-British monarch. Iraq begins to receive support from the Soviets. Iraq will maintain close ties with the Soviets throughout the Cold War.
August: Thor IRBM deployed to the UK, within striking distance of Moscow.
July 24: During the opening of the American National Exhibition in Moscow US Vice President Richard Nixon and Soviet Premier Nikita Khrushchev openly debate the capacities of each Superpower. This conversation is known as the Kitchen Debate.
December: Formation of the FNL (pejoratively called Viet Cong) in North Vietnam. It is a Communist insurgent movement that vows to overthrow the anti-communist South Vietnamese dictatorship. It is supplied extensively by North Vietnam and the USSR eventually.
June: Sino-Soviet split: The Chinese leadership, angered at being treated as the "junior partner" to the Soviet Union, declares its version of Communism superior and begin to compete with the Soviets for influence, thus adding a third dimension to the Cold War.
July 20: Neutralization of Laos is established by international agreement, but North Vietnam refuses to withdraw its personnel.
September 8: Himalayan War: Chinese forces attack India, making claims on numerous border areas.
October 16: Cuban Missile Crisis: The Soviets have secretly been installing military bases, including nuclear weapons, on Cuba, some 90 miles from the US mainland. Kennedy orders a "quarantine" (a naval blockade) of the island that intensifies the crisis and brings the US and the USSR to the brink of nuclear war. In the end, both sides reach a compromise. The Soviets back down and agree to withdraw their nuclear missiles from Cuba, in exchange for a secret agreement by Kennedy pledging to withdraw similar American missiles from Turkey, and guaranteeing that the US will not move against the Castro regime.
November 21: End of the Himalayan War. China occupies a small strip of Indian land.
August 5: The Partial Test Ban Treaty is signed by the US, UK and USSR, prohibiting the testing of nuclear weapons anywhere except underground.
November 2: South Vietnamese Prime Minister Ngo Dinh Diem is assassinated in coup. CIA involvement is suspected.
November 22: John F. Kennedy is shot and killed in Dallas. There has been some speculation over whether communist countries or even CIA were involved in the assassination, but those theories remain controversial. Kennedy's vice-president Lyndon B. Johnson becomes President of the United States.
October 22: Egypt defects to the American camp by accepting a U.S. cease-fire proposal during the October 1973 war.
November 11: The Soviet Union announces that, because of its opposition to the recent overthrow of the government of Chilean President Salvador Allende, it will not play a World Cup Soccer match against the Chilean team if the match is held in Santiago.
April 30: North Vietnam wins the war in South Vietnam. The South Vietnam regime falls with the surrender of Saigon and the two countries are united under a Communist government.
May 12: Mayagüez incident: The Khmer Rouge seize an American naval ship, prompting American intervention to recapture the ship and its crew. In the end, the crew is released from captivity.
June 25: Portugal withdraws from Angola and Mozambique, where Marxist governments are installed, the former with backing from Cuban troops. The Civil war engulfs both nations and involves Angolans, Mozambicans, South Africans, and Cubans, with the superpowers supporting their respective ideologies.
July: The Apollo-Soyuz Test Project takes place. It is the first joint flight of the US and Soviet space programs. The mission is seen as a symbol of détente and an end to the "space race".
December 12: NATO Double-Track Decision - NATO offers mutual limitation of ballistic missiles combined with the threat that in case of disagreement NATO would deploy more middle-range nuclear weapons in Western Europe.
August 31: In Poland the Gdańsk Agreement is signed after a wave of strikes which began at the Lenin Shipyards in Gdańsk. The agreement allows greater civil rights, such as the establishment of a trade union independent of communist party control.
January 17: Martial law was lifted by Ferdinand Marcos in preparation for the visit of Pope John Paul II.
January 20: Ronald Reagan inaugurated 40th President of the United States. Reagan is elected on a platform opposed to the concessions of détente.
January 20: Iran hostage crisis ends.
August 19: Gulf of Sidra Incident: Libyan planes attack U.S. jets in the Gulf of Sidra, which Libya has illegally annexed. Two Libyan jets are shot down; no American losses are suffered.
October 27: A Soviet submarine, the U137, runs aground not far from the Swedish naval base at Karlskrona.
November 23: The U.S. Central Intelligence Agency (CIA) begins to support anti-Sandinista Contras.
December 13: Communist Gen. Jaruzelski introduces martial law in Poland, which drastically restricts normal life, in an attempt to crush the Solidarity trade union and the political opposition against communist rule.
July 7: Ten-year-old Samantha Smith accepts the invitation of Soviet premiere Yuri Andropov and visits the Soviet Union with her parents. Smith had written to Andropov to ask if he would "vote to have a war or not?" Smith's letter, published in the Soviet newspaper Pravda, prompted Andropov to reply and invite the girl to the U.S.S.R. The widely publicized event leads to other Soviet-American cultural exchanges.
September 26: The U.S.S.R. nuclear early warning system reports launch of multiple U.S.intercontinental ballistic missiles. Stanislav Yevgrafovich Petrov, an officer of the Soviet Air Defence Forces, correctly identifies them as false alarms. This decision is seen as having prevented a retaliatory nuclear attack based on erroneous data on the United States and its NATO allies, which likely would have resulted in nuclear war and the deaths of hundreds of millions of people.
October 25: U.S. forces invade the Caribbean island of Grenada in an attempt to overthrow the Marxist military government, expel Cuban troops, and abort the construction of a Soviet-funded airstrip.
November 2: Exercise Able Archer 83 — Soviet anti-aircraft misinterpret a test of NATO's nuclear warfare procedures as a fake cover for an actual NATO attack; in response, Soviet nuclear forces are put on high alert.
August 11: During a microphone sound check for his weekly radio address, President Ronald Reagan jokes about bombing the Soviet Union. "My fellow Americans," Reagan says. "I'm pleased to tell you today that I've signed legislation that will outlaw Russia forever. We begin bombing in five minutes." The quip is not aired but is leaked to the press. The Soviet Union temporarily puts its defense forces on high alert.
March 11: Mikhail Gorbachev becomes leader of the Soviet Union.
August 6: Coinciding with the 40th anniversary of the atomic bombing of Hiroshima and Nagasaki, the Soviet Union begins what it has announced is a 5-month unilateral moratorium on the testing of nuclear weapons. The Reagan administration dismisses the dramatic move as nothing more than propaganda and refuses to follow suit. Gorbachev declares several extensions, but the United States fails to reciprocate, and the moratorium comes to an end on February 5, 1987.
November 21: Reagan and Gorbachev meet for the first time at a summit in Geneva, Switzerland, where they agree to two (later three) more summits.
November 3: Iran-Contra affair: The Reagan administration publicly announces that it has been selling arms to Iran in exchange for hostages and illegally transferring the profits to the Contra rebels in Nicaragua.
January 16: Natives within the Party who oppose his policies of economic redevelopment (Perestroika). It is Gorbachev's hope that through initiatives of openness, debate and participation, that the Soviet people will support Perestroika.
December 8: The Intermediate-Range Nuclear Forces Treaty is signed in Washington, D.C. by U.S. President Ronald Reagan and Soviet leader Mikhail Gorbachev. Some later claim this was the official end of the Cold War. Gorbachev agrees to START I treaty.
May 29-June 1: Reagan and Gorbachev meet in Moscow. INF Treaty ratified. When asked if he still believes that the Soviet Union is still an evil empire, Reagan replies he was talking about "another time, another era."
November 6: Soviet scientist and well-known human rights activist Andrei Sakharov begins a two-week visit to the United States.
December 7: Gorbachev announces in a speech to the United Nations General Assembly that the Soviet Union will no longer militarily interfere with Eastern Europe.
December 22: South Africa withdraws from South West Africa (Namibia).
November 9: Revolutions of Eastern Europe: Soviet reforms have allowed Eastern Europe to change the Communist governments there. The Berlin Wall is breached when Politburo spokesman, Günter Schabowski, not fully informed of the technicalities or procedures of the newly agreed lifting of travel restrictions, mistakenly announces at a news conference in East Berlin that the borders have been opened.