On August 21

Passengers on a Thalys train from Amsterdam to Paris confronted and subdued an attacker who attempted a mass shooting.

Syrian civil war: Areas controlled by the Syrian opposition in Ghouta, Damascus, were attacked by rockets (launcher pictured) containing sarin, killing at least 281 people.

BioShock was released in North America, becoming a critical success and a demonstration of video games as an art form.

A limnic eruption of Lake Nyos in Cameroon released a cloud of carbon dioxide, suffocating 1,746 people and 3,500 livestock.

Six people were killed during an escape attempt and riot at San Quentin State Prison in California; the subsequent trial of six inmates was the longest in state history at the time.

South Vietnamese special forces loyal to Ngô Đình Nhu, the brother of President Ngô Đình Diệm, raided and vandalised Buddhist pagodas (one pictured) across the country, arresting thousands and leaving hundreds dead.

American physicist Harry Daghlian accidentally dropped a tungsten carbide brick onto a plutonium bomb core, exposing himself to neutron radiation and later becoming the first Manhattan Project fatality due to a criticality accident.

World War II: A combined Canadian–Polish force captured the town of Falaise, France, in the final offensive of the Battle of Normandy.

World War II: The Imperial Japanese Army lost the Battle of the Tenaru, the first of its three major land offensives during the Guadalcanal campaign.

Leonardo da Vinci's Mona Lisa (pictured) was stolen from the Louvre by museum employee Vincenzo Peruggia and was not recovered until two years later.

Peninsular War: British and Portuguese forces put an end to the first French invasion of Portugal at the Battle of Vimeiro.

The national colours of Italy first appeared on a tricolour cockade in Genoa.

Austro-Turkish War: Austrian troops under Prince Eugene of Savoy captured the strategically important city of Belgrade from the Ottoman Empire.

Seventh Ottoman–Venetian War: Ottoman forces suddenly abandoned their siege of Corfu, allowing the Republic of Venice to preserve its rule over the Ionian Islands.

Jacobite clans clashed with a regiment of Covenanters in the streets of Dunkeld, Scotland.