Zinn said his experience as a wartime bombardier, combined with his research into the reasons for, and effects of the bombing of Royan and Pilsen, sensitized him to the ethical dilemmas faced by G.I.s during wartime. Zinn questioned the justifications for military operations that inflicted massive civilian casualties during the Allied bombing of cities such as Dresden, Royan, Tokyo, and Hiroshima and Nagasaki in World War II, Hanoi during the War in Vietnam, and Baghdad during the war in Iraq and the civilian casualties during bombings in Afghanistan during the current war there. In his pamphlet, "Hiroshima: Breaking the Silence" written in 1995, he laid out the case against targeting civilians with aerial bombing.