It has been alleged that the British used chemical weapons in Mesopotamia in 1920, during the Iraqi revolt (Ath Thawra al Iraqiyya al Kubra), in the period of the British Mandate over Mesopotamia. Use of tear gas and lethal poison gas against Iraqi rebels was considered, and the use of gas was promoted by Winston Churchill, head of the War Office, who encouraged research into the dropping of mustard gas by air. Tear gas artillery shells were transported to Iraq and approval was given for their use, but tests by the army found them to be impractical and they were not used in combat. Efforts to develop gas weapons for use in Iraq were halted by the British over concerns about embarrassing political repercussions following the signing of the Washington Disarmament Treaty, which contained a pr