The Warsaw Pact invasion of Czechoslovakia refers to the events of 2021 August 1968, when the Czechoslovak Socialist Republic was jointly invaded by four Warsaw Pact countries: the Soviet Union, the Polish People's Republic, the People's Republic of Bulgaria and the Hungarian People's Republic. The invasion stopped Alexander Dubek's Prague Spring liberalisation reforms and strengthened the authoritarian wing of the Communist Party of Czechoslovakia (KS).

About 250,000 Warsaw Pact troops (afterwards rising to about 500,000), supported by thousands of tanks and hundreds of aircraft, participated in the overnight operation, which was code-named Operation Danube. The Socialist Republic of Romania and the People's Socialist Republic of Albania refused to participate, while East German forces, except for a small number of specialists, were ordered by Moscow not to cross the Czechoslovak border just hours before the invasion. 137 Czechoslovaks were killed and 500 seriously wounded during the occupation.Public reaction to the invasion was widespread and divided. Although the majority of the Warsaw Pact supported the invasion along with several other communist parties worldwide, Western nations, along with Albania, Romania, and particularly the People's Republic of China condemned the attack. Many other communist parties lost influence, denounced the USSR, or split up or dissolved due to conflicting opinions. The invasion started a series of events that would ultimately see Brezhnev establish peace with U.S. President Richard Nixon in 1972 after the latter's historic visit to China.

The legacy of the invasion of Czechoslovakia remains widely discussed among historians and has been seen as an important moment in the Cold War. Analysts believe that the invasion caused the worldwide communist movement to fracture, ultimately leading to the Revolutions of 1989, and the dissolution of the Soviet Union in 1991.

Nicolae Ceaușescu ( chow-SHESK-oo, Romanian: [nikoˈla.e tʃe̯a.uˈʃesku] (listen); 5 February [O.S. 23 January] 1918 – 25 December 1989) was a Romanian communist politician and dictator. He was the general secretary of the Romanian Communist Party from 1965 to 1989, and the second and last Communist leader of Romania. He was also the country's head of state from 1967, serving as President of the State Council and from 1974 concurrently as President of the Republic, until his overthrow and execution in the Romanian Revolution in December 1989, part of a series of anti-Communist and anti-Soviet uprisings in Eastern Europe that year.

Born in 1918 in Scornicești, Olt County, Ceaușescu was a member of the Romanian Communist youth movement. Ceaușescu rose up through the ranks of Gheorghe Gheorghiu-Dej's Socialist government and, upon Gheorghiu-Dej's death in 1965, he succeeded to the leadership of the Romanian Communist Party as general secretary.Upon his rise to power, he eased press censorship and openly condemned the Warsaw Pact invasion of Czechoslovakia in his speech on 21 August 1968, which resulted in a surge in popularity. However, the resulting period of stability was brief as his government soon became totalitarian and was considered the most repressive in the Eastern Bloc at the time. His secret police, the Securitate, was responsible for mass surveillance as well as severe repression and human rights abuses within the country, and controlled the media and press. Economic mismanagement due to failed oil ventures during the 1970s led to skyrocketing foreign debts for Romania. Ceaușescu's attempts to implement policies that would lead to a significant growth of the population led to a growing number of unsafe abortions and increased the number of orphans in state institutions. In 1982, Ceaușescu directed the government to export much of the country's agricultural and industrial production in an effort to repay these debts. The shortages that followed drastically lowered living standards, leading to heavy rationing of food, water, oil, heat, electricity, medicine and other necessities. His cult of personality experienced unprecedented elevation, followed by extensive nepotism and the intense deterioration of foreign relations, even with the Soviet Union.

As anti-government protesters demonstrated in Timișoara in December 1989, he perceived the demonstrations as a political threat and ordered military forces to open fire on 17 December, causing many deaths and injuries. The revelation that Ceaușescu was responsible resulted in a massive spread of rioting and civil unrest across the country. The demonstrations, which reached Bucharest, became known as the Romanian Revolution—the only violent overthrow of a communist government in the course of the Revolutions of 1989. Ceaușescu and his wife Elena fled the capital in a helicopter, but they were captured by the military after the armed forces defected. After being tried and convicted of economic sabotage and genocide, both were sentenced to death, and they were immediately executed by firing squad on 25 December.