 Complete the following phrase:  During all parts of the war, use of chemical and biological weapons were extremely limited by both sides. Italy used mustard gas and phosgene during the short Second Italo-Abyssinian War, Germany employed chemical agents such as Zyklon B against Jews, political prisoners and other victims in extermination camps during the Holocaust, and Japan employed chemical and biological weapons in China. In 1943 a U.S. ship carrying a secret Chemical Warfare Service cargo of mustard gas as a precautionary retaliatory measure was sunk in an 