How did the Allies act passively at the onset of German aggression under Hitler? Why?
This is referred to as an appeasement, which means an attempt to bring about a state of peace, quiet, ease, or calm. In history, however, the word usually refers to the unsuccessful effort by British Prime Minister, Neville Chamberlain to keep Adolph Hitler from starting World War II. The term is most often applied to the foreign policy of the UK governments of Prime Ministers Ramsay MacDonald, Stanley Baldwin and Neville Chamberlain towards Nazi Germany from 1933 and Fascist Italy established in 1922 between 1935 and 1939.
At the beginning of the 1930s, appeasing concessions were widely seen as desirable due to the anti-war reaction to the trauma of World War I (1914–1918), second thoughts about the vindictive treatment of Germany in the 1919 Treaty of Versailles, and a perception that fascism was a useful form of anti-communism. As alarm grew about the rise of fascism in Europe, Chamberlain resorted to news censorship to control public opinion.
Britain would not enter hostilities for many months, admitting un-readiness to directly oppose Germany in combat. She sat and watched the invasion of France, acting only four years later.