Intelligence reports suggested that the Germans were stocking chemical weapons, including a new chemical agent called Tabun. American President Franklin D. Roosevelt issued a policy statement condemning the use of gas by any civilized nation, but he pledged that the United States would reply in kind if the enemy dared to use such weapons first. John Harvey was selected to convey a shipment of poison gas to Italy to be held in reserve should such a situation occur. When the mustard gas bombs were loaded aboard John Harvey , they looked deceptively conventional. Mustard is a blister gas that irritates the respiratory system and produces burns and raw ulcers on the skin.
Victims exposed to the gas often suffer an agonizing death.
The poison gas shipment was shrouded in official secrecy. Even Knowles was not formally informed about the lethal cargo. Perceptive members of the crew, however, must have guessed the voyage was out of the ordinary. For one thing, 1st Lt. Howard D. Beckstrom of the 701st Chemical Maintenance Company was on board, along with a detachment of six men.