 Complete the following phrase:  At the start of World War II in 1939, following an appeal by Franklin D. Roosevelt, President of the then neutral United States, the major European powers, including Britain and Germany, agreed not to bomb civilian targets outside combat zones: Britain agreeing provided that the other powers also refrained. see the policy on strategic bombing at the start of the World War II. However, this was not honored, as belligerents of both sides in the war adopted a policy of indiscriminate bombing of enemy cities. Throughout World War II, cities like Chongqing, Warsaw, Rotterdam, London, Coventry, Stalingrad, Hamburg, 