Gruen was born Victor Grunbaum in a middle-class Jewish family in [[Vienna]]. He trained as an architect but also devoted much of his youthful energy to producing ansd acting in political cabarets in the interwar Austrian capital. As a Jew, and a known social democrat, he appreciated the danger he was in following the German [[Anschluss]] of Austria in 1938 - he was briefly arrested by the Nazi authorities and released only after friends gave a bribe - and fled the country with his wife, travelling via Zurich and London to [[New York City]]. There he recommenced working as an architect, initially on high-class Fifth Avenue shops. During the war (in which he applied to join, but was rejected by, the US Army), he became a naturalised American citizen and changed his surname to Gruen.