After graduating from a classical gimnazjum in Lwów, Wittlin joined the volunteer military formation of the Polish Legion in August 1914.

With his friend Joseph Roth he again joined the Austrian army in 1916, and after some military training was drafted into the infantry.

Shortly before being sent to the Italian front he fell ill with scarlet fever and was thus prevented from direct participation in the fighting.

His military service took place far away from the front and included among other things working as a translator in prisoner-of-war camps with Italian soldiers.

With the help of Hermann Kesten, he and his family succeeded in escaping in January 1941 from Nice through Spain and Portugal to New York, where he remained after the war.