Mustard gas

Mustard gas is a highly corrosive and toxic chemical used as a poison gas.

Mustard Gas in Southern Victory
By the end of the Great War, both the Entente and the Central Powers had taken to using mustard gas loaded into artillery shells as a weapon. By the Second Great War, nerve agents were the more common weapon of choice.

Mustard Gas in World War
In 1943, British Prime Minister Winston Churchill used stockpiles of mustard gas--which he had been stockpiling in anticipation of a German invasion of Britain in World War II, a war in which poison gas was banned--to repel the Race's invasion of Britain. Mustard gas devastated unprepared Lizard forces and permanently broke the back of an invasion that had already been faltering in the face of stiff British resistance. From then till the end of the conflict, mustard gas and other poison gases were used by other Tosevite not-empires.