1920-21 during which the use of tear gas in the course of military operations had been the stated policy of the British Government," Douglas writes. "In both cases practical difficulties rather than moral qualms …prevented their use."

Before 1920, the British War Cabinet had expressly denied requests by field commanders to use tear gas in occupied Mesopotamia. That changed in June 1920, when an organized Arab rebellion erupted. Winston Churchill, then War Secretary and a vocal advocate of nonlethal gas use, gave commanders in the field permission to use "existing stocks" of tear gas artillery shells.

But at that time, there were no existing stocks of such weapons in Mesopotamia. The nearest supply was in Egypt and needed to be transported to the region. By the time they arrived, therebellion was over and the shells went unused.

Anticipating renewed hostilities, a Royal Air Force commander sought permission in 1922 to convert the unused artillery shells into bombs that could be dropped from aircraft. Churchill signed off on the request, but was forced to rescind his permission just days later when the Washington Disarmament Conference passed a resolution banning the use of tear gas. The shells, again, went unused.

There is little doubt had the timing of these events been slightly different -- had the 1920 rebellion lasted longer or if there had been time to convert the shells to aerial bombs -- that British forces would have used their chemical ordnance. And that, says Douglas, may have vastly changed the course of history. Churchill had given authorization to use