After completing Volksschule, Grimm attended the non-commissioned officers' school in Fürstenfeldbruck from 1906 to 1909, and then entered the 14th Royal Bavarian Infantry Regiment.
[2] When the Nazi Party was re-established after being outlawed in the aftermath of the Beer Hall Putsch, Grimm rejoined on 27 February 1925.
In January 1934, its name was changed to Oberstes Parteigericht (Supreme Party Court) though it was more of an arbitration and mediation organization, rather than a strictly legal one.
[6] Beginning in August 1941, he served in the German army on the Eastern Front as a battalion commander with the rank of Hauptmann before returning to Germany in 1943 due to illness.
[7] According to documents released by The Wilson Center in 2019, Grimm was implicated in the 20 July 1944 plot to assassinate Hitler, and was killed the next day in reprisal.