The Cold War was a major part of the second half of the 20th century, as tensions arose between two of the world's biggest superpowers over differences in both ideology and philosophy.
Given the name because there was no large-scale fighting directly between the two, the USA and USSR, they instead supported major regional conflicts in various proxy wars.
The struggle for geopolitical dominance between the USA and USSR would instead often flare up indirectly, famously doing so as propaganda campaigns, espionage, rivalry at sports events and in technological competitions such as the Space Race.
The Cold War came to an end until 1991 with the collapse of the USSR, forever changing the world order and ushering in the next era of world politics.
Origins of the Cold War
Following the end of the Second World War and the surrender of the Nazis in 1945, the uneasy alliance of the United States, the UK and USSR began to unravel.
By 1948 the Soviets had installed governments in all the Eastern European states liberated by the Red Army.
Fearing permanent Soviet dominance in the region, the Americans and British began to take action to prevent the spread of communism to western European countries.
The Cold War had fully formed by 1947 when US aid provided under the Marshall Plan to western Europe had brought those helped in line with American influence and the Soviets had fully installed openly communist regimes in eastern Europe.
The two sides of the conflict had drawn lines in the sand and the power struggle had properly begun.
Struggle between superpowers
The Cold War would reach its peak in 1948-53. During this period the Soviets blockaded the Western-held sectors of West Berlin unsuccessfully and the US and its European allies formed the North Atlantic Treaty Organization (NATO).
In that same window, the USSR exploded its first nuclear warhead, ending the American monopoly on the weapons and the Chinese Communist Government came into power, ramping up the geopolitical pressure.
Although never culminating in all-out war, these dominating superpowers instead won influence through a series of smaller proxy wars.
One of the earliest and most famous is when both sides exerted influence over the civil war in Korea after the Soviet-supported communist government of North Korea invaded the US-supported South Korea, ending in a tense stalemate three years later.
The death of long-time Russian dictator Stalin would temporarily ease tensions between the two, although the standoff remained.
The next period of high tension came in between 1958 and 1962, a span of time involving a crisis so severe it almost led to major conflict.
Both the US and the Soviets began developing intercontinental ballistic missiles and in 1962, the secret installation of them in Cuba brought US cities very obviously in range of devastation.
This led to one of the most famous diplomatic crises in US history, the Cuban Missile Crisis, which only ended when both sides reached an agreement to withdraw the missiles.
Although soon afterward, both sides would sign a ban on nuclear weapons testing, the event would reinforce the determination of both sides and see the beginning of a 25-year build-up of both conventional and strategic forces.
A new era
During the 1960s and 1970s the Cold War would become more complicated, as it became more difficult to define the allegiance of countries by simple blocs of influence.
Instead, the world was more obviously defined by sets of complex patterns of international relationships.
China split with the Soviet Union in 1960 and the divide was growing, while economic growth in the West reduced any reliance on the United States.
Traditionally less powerful countries were gaining independence and becoming much harder for either side to coerce.
Spycraft between the nations remained rife as a mutual distrust and constant fear of nuclear war led to paranoia and suspicion.
A British mission of spies, known as BRIXMIS, was able to send 31 members of personnel into East Germany to keep an eye on the USSR.
The 1970s saw another temporary bout of easing tensions as demonstrated by the Strategic Arms Limitation Talks (SALT) that led to the SALT I and II agreements of 1972 and 1979.
These agreements saw the two superpowers set limits on their anti-ballistic missiles and on their strategic missiles capable of carrying nuclear weapons.
What followed was the last period of real tension between the two superpowers, expressing itself during the 1980s through a massive arms buildup and a competition for influence in the Third World.
But the rivalry began to break down in the later years of the decade as under Mikhail Gorbachev the Soviets began weakening the country's more totalitarian aspects.
His efforts to change the system this way also came as communist regimes in the Eastern European bloc began to collapse.
The rise of democratic governments in East Germany, Poland, Hungary and Czechoslovakia were quickly followed by the reunification of Germany under NATO with Soviet approval.
In late 1991 the Soviet Union finally collapsed and 15 new independent nations were born from its territory, Russia soon elected a leader democratically to office, and the Cold War was over.
Key moments of the Cold War
4-11 February: Yalta Conference meeting of FDR, Churchill, Stalin – the 'Big Three'. The Cold War Begins.
9 February: Stalin hostile speech – communism and capitalism were incompatible.
5 March: Iron Curtain Speech by Winston Churchill – "an 'iron curtain' has descended on Europe".
10 March: Truman demands Russia leaves Iran.
1 July: Operation Crossroads with Test Able was the first public demonstration of America's atomic arsenal.
2 September: Rio Pact – The US meets Latin American countries and creates a security zone around the hemisphere.
25 February: Communist takeover in Czechoslovakia.
2 March: Truman's Loyalty Program created to catch Cold War spies.
17 March: Brussels Pact organised to protect Europe from communism.
24 June: Berlin Blockade begins, lasting 11 months.
4 April: NATO ratified.
29 August: Russia tested its first atomic bomb.
1 October: Communists take control of China and establish the People's Republic of China.
Watch: Our documentary on BRIXMIS - the Cold War British spies who kept an eye on the Soviet Union.
24 June: Korean War begins. Stalin supports North Korea which invades South Korea equipped with Soviet weapons.
A-bombs developed by Britain.
March: CIA helps overthrow regimes in Iran and Guatemala.
May: Warsaw Pact formed.
29 June: USSR sends tanks into Poznan, Poland, to suppress demonstrations by workers.
October-November: Rebellion put down in Communist Hungary.
4 October: Sputnik launched into orbit.
3 November: Sputnik II launched – space dog Laika died in space.
31 January: Explorer I launched.
November: Khrushchev demands withdrawal of troops from Berlin.
January: Cuba taken over by Fidel Castro.
May: Soviet Union reveals that US spy plane was shot down over Soviet territory.
November: John F. Kennedy elected President of USA.
19 December: Cuba openly aligns itself with the Soviet Union and its policies.
13 August:Berlin border is closed.
17 August: Construction of Berlin Wall begins.
October: Cuban Missile Crisis.
22 November: President Kennedy assassinated in Dallas, Texas.
August: Soviet Red Army crushes Czechoslovakian revolt.
20 July: Apollo 11 lands on the moon.
July: SALT I treaty signed.
January: Ceasefire in Vietnam between North Vietnam and United States.
September: US-supported coup overthrows Chilean government.
October: Egypt and Syria attack Israel. Egypt requests Soviet aid.
17 April: North Vietnam defeats South Vietnam, which falls to Communist forces.
January: US and China establish diplomatic relations.
July: SALT II treaty signed.
November: Shah of Iran overthrown. Iranian Hostage Crisis.
December: Soviet forces invade Afghanistan.
October: US troops invade and overthrow regime in Grenada.
Mikhail Gorbachev becomes leader of the Soviet Union initiating a campaign of openness and restructuring.
October: President Reagan and Gorbachev resolve to remove all intermediate nuclear missiles from Europe.
December: Reagan and Gorbachev sign the INF Treaty, agreeing to remove their "intermediate-range and shorter-range missiles". The agreement would continue for more than 30 years, until the withdrawal of both the United States and Russia.
January: Soviet troops withdraw from Afghanistan.
June: Poland becomes independent.
September: Hungary becomes independent.
November: Berlin Wall is demolished and East Germany allows unrestricted migration to West Germany.
December: Communist governments fall in Czechoslovakia, Bulgaria, and Romania.
March: Lithuania becomes independent.
29 May: Boris Yeltsin elected as President of Russia.
3 October: Germany reunited.
August: End of Soviet Union and the Cold War Ends.
Read more about the Cold War here.
Cover image: Alamy.