Conversation so far:
When did Josef Mengele join the military?
Mengele joined the Nazi Party in 1937 and the Schutzstaffel (SS; protection squadron) in 1938.
What was his rank?
he served with the rank of SS-Untersturmfuhrer (second lieutenant) in a medical reserve battalion until November 1940.
What did he do after 1940?
He was next assigned to the SS-Rasse- und Siedlungshauptamt (SS Race and Resettlement Main Office) in Posen, evaluating candidates for Germanisation.

Question: What is germanisation.?
Self-contained rewrite: What is Germanisationin relation to Josef Mengele?