 The simultaneous Invasion of Poland by Nazi Germany and the Soviet Union, launched in September 1939, had triggered the Second World War, and shortly after passing his law exams he received call-up papers requiring him to join the army.However, in the end Gerstner was spared from military service as a result of injuries caused by childhood polio.At the same time the Foreign Ministry offered him a job based on his mastery of the French language, and in April 1940 he started work as a translator in the ministry's radio department.