Gas had been used by the Germans already, on the Eastern Front, at Bolimov, on 3 January, when gas-filled shells had been fired into the Russian positions on the River Rawka west of Warsaw. The chemical agent, known to the Germans as T-Stoff (xylyl bromide), was lachrymatory (tear-producing), not lethal. It appears to have troubled the Russians not at all; prevailing temperatures were so low that the chemical froze instead of vaporising.28 By April, however, the Germans had a killing agent available in quantity, in the form of chlorine.
