lehmann was born in strasbourg, alsace-lorraine in 1917 to a family of ashkenazi jewish ancestry. he grew up in frankfurt am main, germany, until the machtergreifung in 1933 his family fled to switzerland to escape the nazis. he graduated from high school in zurich, and studied mathematics for two years at trinity college, cambridge. following that, he emigrated to the united states, arriving in new york in late 1940. he enrolled in university of california, berkeley as a post-graduate student—albeit without a prior degree—in 1941.