German Chancellor for 100 days (July-Oct 1917) who had been chosen by Ludendorff to replace Bethmann-Hollweg and form a new government. He had previously headed the Department for Grain Supply (1915) and was the Commissioner for Food Supply (1917). A born commoner who was completely unqualified for the chancellorship, Kaiser Wilhelm II thought he was "too soft;" the military eventually withdrew their support and he was forced to resign. Later headed the administration of Pomerania.

Michaelis was married to Margarete Schmidt with whom he had five daughters and two sons. He died on 24 July 1936 in Bad Saarow, Mark Brandenburg.