World War II: A Luftwaffe bombing raid on the harbour of Bari, Italy, sinks numerous cargo and transport ships, including the American SS John Harvey, which is carrying a stockpile of mustard gas.

The air raid on Bari was an air attack by German bombers on Allied forces and shipping in Bari, Italy, on 2 December 1943, during World War II. 105 German Junkers Ju 88 bombers of Luftflotte 2 surprised the port's defenders and bombed shipping and personnel operating in support of the Allied Italian Campaign, sinking 27 cargo and transport ships, as well as a schooner, in Bari harbour.

Bari is the capital city of the Metropolitan City of Bari and of the Apulia region, on the Adriatic Sea in southern Italy. It is the most important economic centre of mainland southern Italy. It is a port and university city as well as the city of Saint Nicholas. The city itself has a population of 315,473 inhabitants, and an area of over 116 square kilometres (45 sq mi), while the urban area has 750,000 inhabitants. Its metropolitan province has 1.2 million inhabitants.

SS John Harvey was a U.S. World War II Liberty ship. This ship is known for carrying a secret cargo of mustard gas and whose sinking by German aircraft in December 1943 at the port of Bari in south Italy caused an unintentional release of chemical weapons.

Mustard gas or sulfur mustard are names commonly used for the organosulfur chemical compound bis(2-chloroethyl) sulfide, which has the chemical structure S(CH₂CH₂Cl)₂, as well as other species. In the wider sense, compounds with the substituents −SCH₂CH₂X or −N(CH₂CH₂X)₂ are known as sulfur mustards or nitrogen mustards, respectively, where X = Cl or Br. Such compounds are potent alkylating agents, making mustard gas acutely and severely toxic. Mustard gas is a carcinogen. There is no preventative agent against mustard gas, with protection depending entirely on skin and airways protection, and no antidote exists for mustard poisoning.