History Today: When the Soviet Union invaded Czechoslovakia

August 20 is an important day in history as several notable events took place across the world. The Soviet and Warsaw Pact troops invaded Czechoslovakia in 1968, effectively crushing the liberal reforms of the Prague Spring.

If you are a history geek who loves to learn about important events from the past, Firstpost Explainers’ ongoing series, History Today , will be your one-stop destination to explore key events.

In 1975, Nasa launched its ambitious Viking missions designed to explore Mars and search for signs of life. On this day in 1944, former Prime Minister of India Rajiv Gandhi was born. His birth anniversary is celebrated as Sadbhavana Diwas.

Here is all that happened on this day.

Soviets invaded Czechoslovakia

It was on this day in 1968 that the Soviet and Warsaw Pact troops invaded Czechoslovakia, crushing the liberal reforms of the Prague Spring and reasserting Moscow’s control over the Eastern Bloc. The invasion marked one of the most dramatic confrontations of the Cold War.

Led by Communist Party leader Alexander Dubcek, the Prague Spring sought to create “socialism with a human face” by introducing reforms like greater freedom of the press, speech, and travel, as well as a partial decentralisation of the economy. These changes were wildly popular among the Czechoslovakian people but were viewed with alarm by Moscow and other hardline communist regimes. Soviet leader Leonid Brezhnev and his allies feared that the reforms would undermine communist rule and threaten the stability of the entire Eastern Bloc.

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On the night of August 20–21, approximately 200,000 soldiers and 5,000 tanks from the Soviet Union, Poland, East Germany, Hungary, and Bulgaria crossed into Czechoslovakia. The operation was swift and overwhelming. Despite massive protests and passive resistance, Czechoslovak forces were ordered not to resist militarily, preventing a full-scale war but leaving citizens vulnerable. At least 137 civilians were killed and hundreds were injured during the occupation.

Dubcek and other leaders were arrested and taken to Moscow, where they were pressured into rolling back reforms. A new pro-Soviet leadership soon replaced him, and strict censorship returned. The invasion became a turning point in the Cold War, symbolising the limits of freedom within the Soviet bloc.

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Globally, the move sparked outrage. Western nations condemned the action, though they stopped short of intervention. The event also led to the formulation of the Brezhnev Doctrine, under which the USSR claimed the right to intervene in any socialist state deemed to be straying from orthodoxy.

Nasa launches its ambitious Viking 1 mission

The National Aeronautics and Space Administration (Nasa) launched its most ambitious mission, Viking 1, on August 20, 1975. The launch from Cape Canaveral aboard a Titan IIIE-Centaur rocket marked a bold step in planetary exploration, combining advanced engineering with unprecedented scientific goals.

The Viking program, costing nearly $1 billion, was one of Nasa’s most complex interplanetary undertakings. Viking 1 consisted of two parts: an orbiter to map Mars from above and a lander to conduct on-site experiments. After an 11-month journey covering nearly 500 million kilometres, Viking 1 entered Mars’ orbit in June 1976. On July 20, 1976, exactly seven years after the Apollo 11 Moon landing, the lander touched down on Chryse Planitia, becoming the first successful US spacecraft to land and operate on Mars.

The mission’s goals were groundbreaking - to analyse the Martian soil for biological activity, study the atmosphere, and capture high-resolution images of the surface. Viking 1 sent back stunning photographs of barren landscapes, red deserts, and rocky plains, giving humanity its first close-up view of Mars. Its experiments revealed intriguing but inconclusive chemical reactions in the soil. While not definitive proof of life, these findings shaped decades of debate about the planet’s habitability.

Birth of Rajiv Gandhi

Every year, August 20 is celebrated as Sadbhawana Diwas or Harmony Day, a day when Rajiv Gandhi , the eldest son of then Prime Minister Indira Gandhi and Feroze Gandhi, was born. As the grandson of Jawaharlal Nehru, Rajiv grew up surrounded by politics but initially showed little inclination toward it.

Educated at Doon School, Dehradun, he later went abroad to study at Trinity College, Cambridge, and then Imperial College, London. Unlike his mother and younger brother, Sanjay Gandhi, Rajiv preferred a quiet life. He trained as a commercial pilot and worked with Indian Airlines, enjoying a career away from the political spotlight.

However, destiny drew him into politics after the tragic death of his brother, Sanjay, in a plane crash in 1980. Pressured by party members and his mother, Rajiv reluctantly entered public life and contested elections from Amethi, Uttar Pradesh. He quickly gained popularity for his soft-spoken demeanour and modern outlook.

Following the assassination of Indira Gandhi in October 1984, Rajiv Gandhi was sworn in as India’s youngest Prime Minister at the age of 40. His tenure was marked by efforts to modernise India, particularly through technology, computers, and telecommunications. He was also instrumental in strengthening India’s relations abroad and pushing for economic reforms.

This Day, That Year

• Senegal seceded from the Mali Federation, declaring its full independence on this day in 1960.

• In 1920, the National Football League was formed at a meeting in Canton, Ohio.

• Labour activists closed the entire Port of London in the London Dock Strike in 1889.

With inputs from agencies