August 21

Rocket launcher from the Ghouta chemical attack

• 1716 – 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.
• 1945 – 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.
• 1971 – 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.
• 1986 – A limnic eruption of Lake Nyos in Cameroon released a cloud of carbon dioxide, suffocating 1,746 people and 3,500 livestock.
• 2013 – 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.