<P> Britain made plans to use mustard gas on the landing beaches in the event of an invasion of the United Kingdom in 1940 . The United States considered using gas to support their planned invasion of Japan . </P> <P> The contribution of gas weapons to the total casualty figures was relatively minor . British figures, which were accurately maintained from 1916, recorded that 3% of gas casualties were fatal, 2% were permanently invalid and 70% were fit for duty again within six weeks . </P> <P> It was remarked as a joke that if someone yelled' Gas', everyone in France would put on a mask...Gas shock was as frequent as shell shock . </P> <P> Gas! GAS! Quick, boys!--An ecstasy of fumbling, Fitting the clumsy helmets just in time; But someone still was yelling out and stumbling, And flound'ring like a man in fire or lime...Dim, through the misty panes and thick green light, As under a green sea, I saw him drowning . In all my dreams, before my helpless sight, He plunges at me, guttering, choking, drowning . </P>

What type of gas was used in ww1