His studies were interrupted by World War I, during which Trier served in the Imperial German Army.

Trier was infected by malaria in 1916, and was subsequently interned in Switzerland, where he was able to continue his studies at the University of Basel (1916-1918).

After the war, he continued his studies at the universities of Berlin (1918-1919) and Marburg (1919-1920), and subsequently worked as a secondary school teacher.

Trier gained his PhD at the University of Freiburg in 1923 with a thesis on ethnology, etymology and culture.

A teacher and lecturer of considerable ability, Trier played an instrumental role in reviving the field of German studies after World War II.