On 6 November 1941 Heinrich Himmler appointed Altagayer an SS-Hauptsturmführer and on 9 November 1943 he was promoted to SS-Sturmbannführer. In 1942, Altgayer was selected as one of two representatives of the German minority in Sabor. In 1943 he was named as secretary to the Ustaše government and responsible for the internal affairs of the German minority. The leader of the NDH, Ante Pavelić, also appointed Altgayer as a reserve colonel in the Ustaše Militia and he was also bestowed with the title "Knight" (vitez). He served briefly on the German Eastern Front.
