Chemical weapons and the United Kingdom
Chemical weapons were widely used by the United Kingdom in World War I. The use of poison gas was suggested by Winston Churchill and others in Mesopotamia during the interwar period, and also considered in World War II, although it appears that they were not actually used in these conflicts. While the UK was a signatory of the Hague Conventions of 1899 and 1907 which outlawed the use of poison gas shells, the conventions omitted mention of deployment from cylinders.
Source: Wikipedia — Chemical weapons and the United Kingdom (CC BY-SA 4.0)