His dissertation, Über die Zerlegung der endlichen Gruppen in indirekte unzerlegbare Faktoren ("On the decomposition of a finite group into indirect indecomposable factors") established that any two decompositions of a finite group into a direct product are related by a central automorphism.

He also anticipated the role played by digital computers in numerical solution of systems of linear equations.

Remak's analysis may have influenced John von Neumann, who was a fellow lecturer in Berlin, but most of it has not been translated into English and it remains little known and appreciated in the English-speaking world.

After the Nazis seized power in 1933 and the Civil Service Law was passed a few months later, Remak, who was of Jewish ancestry, lost his right to teach in September 1933.

After an unsuccessful campaign by his wife to secure a permission for him to emigrate to the United States, he was released and permitted to leave for Amsterdam.