Alleged British use of chemical weapons in Mesopotamia in 1920 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 . It is clear that the use of tear gas , rather than a lethal gas , was considered , as a War Office minute of 12 May 1919 , shows , in which Winston Churchill argued British policy . The British " Manual of Military Law " stated that the rules of war applied only to conflict " between civilized nations . " Already in the " Manual " of 1914 , it was clearly stated that " they do not apply in wars with uncivilized States and tribes " . Some gas shells and protective clothing were shipped to India in July 1919 , with a further small shipment in January 1920 , for use on the North - West Frontier . However , a requisition for 16 , 000 shells and 10 , 000 gas masks was blocked by Lord Sinha , the Under - Secretary of State for India . He believed that a first use of chemical weapons by British / Indian forces would have serious implications , both moral and political , and that chemical weapons should only be used in retaliation for an Afghan or North - West Frontier Tribal chemical attack . In India , a temporary Travelling Gas School was set up in September 1920 , but thereafter the matter lapsed . Britain had used gas weapons in the Middle East before , most notably in the Second Battle of Gaza against Ottoman forces in World War I . On that occasion , the use of gas did not prevent a British military defeat . Work of recent historians . There is little evidence that gas was actually used or , if it was , that the gas involved was lethal and not tear gas . In March , 1992 , United States Congressman Henry B . Gonzalez , speaking in the House of Representatives , said that Britain used gas against the Kurds ; and his statement was much quoted in following years . The main source usually quoted in support of the idea that Britain used poison gas in Mesopotamia is Geoff Simons , " Iraq : From Sumer to Saddam " ( 1994 ) , who says " gas was used against the Iraqi rebels in 1920 . " In the third edition of his book , " Iraq : From Sumer to post - Saddam " ( 2004 ) Simons wrote : " In the event , gas was used against the Iraqi rebels in 1920 with ‘ excellent moral effect ’ , though gas shells were not dropped from aircraft because of practical difficulties . " Another historian , Lawrence James , says , " By September the local commander , General Sir Aylmer Haldane , was beginning to get the upper hand , although he was still desperate enough to clamour for large supplies of poison gas . It was not needed , for air power had given his forces the edge whenever the going got tough " . On whether gas was used he writes that : " RAF Officers asked Churchill . . . for use of poison gas . He agreed but it was not used " . Niall Ferguson , in his 2006 book " The War of the World " , writes : " To end the Iraqi Insurgency of 1920 . . . the British relied on a combination of aerial bombardment and punitive village burning expeditions . Indeed , they even contemplated using mustard gas too , though supplies proved unavailable " . Anthony Clayton writes in " The Oxford History of the British Empire " that " [ T ] he use of poisonous gas was never sanctioned " . A December 2009 article in the " Journal of Modern History " by R . M . Douglas of Colgate University went through the known sources and concluded that : " [ W ] hile at various moments tear gas munitions were available in Mesopotamia , circumstances seeming to call for their use existed , and official sanction to employ them had been received , at no time during the period of the mandate did all three of these conditions apply " , and that it was clear that no poison gas was used . Douglas observed that Churchill ' s forceful statement had served to convince observers of the existence of weapons of mass destruction which were not actually there , which ironically matched events in 2003 .