Ramón Mercader, a Spanish-born agent working for Stalin's secret police, gained Leon Trotsky's trust and then attacked him with a mountaineering ice axe in his study in Coyoacán. Despite the wound, Trotsky fought back and survived nearly 24 hours before dying on August 21, 1940, closing out Stalin's decade-long campaign to eliminate his exiled rival.

The Republic of Dahomey formally became independent from France, one of more than a dozen African nations to gain sovereignty during 1960's wave of decolonization. Hubert Maga became the country's first president. The nation would later rename itself Benin in 1975 and endure years of political instability and multiple coups before establishing multiparty democracy in the 1990s.

On the night of August 20, some 200,000 Soviet-led Warsaw Pact soldiers crossed into Czechoslovakia to end Alexander Dubček's liberalizing reforms. Citizens in Prague and Bratislava tried blocking tanks with their bodies and repainting street signs to confuse invaders, but the resistance was unarmed against overwhelming force, and the occupation snuffed out the Prague Spring within days.

Voyager 2 lifted off aboard a Titan-Centaur rocket, sixteen days before its twin Voyager 1, on a trajectory exploiting a rare planetary alignment. Over the next dozen years it became the only spacecraft to visit Uranus and Neptune, returning images that rewrote textbooks on the outer solar system before heading into interstellar space.