From 1903 to 1905 he was assistant to Walter Andrae in the acclaimed excavations of Assur, and later traveled widely in Iraq and Iran at the beginning of the twentieth century.
He surveyed and documented many historical sites in Turkey, Syria, Persia (later Iran) and most importantly in Iraq (e.g. Baghdad, Ctesiphon).
After military service during World War I he was appointed full professor of "Landes- und Altertumskunde des Orients" (approximately: Studies of the Ancient and modern Near East) in Berlin in 1920.
In 1935 he was forced to leave his position in Germany because of his Jewish descent and became a faculty member of Princeton's Institute for Advanced Study from 1936 to 1944.
The material, some 30,000 documents include his field notebooks, photographs, drawings and object inventories from his excavations at Samarra, Persepolis, Pasargadae and elsewhere in Iran, Iraq, Turkey and Syria.