Mengele joined the Nazi Party in 1937. He received his medical degree in 1938, the same year he joined the SS. Mengele was drafted into the army in June 1940, and subsequently volunteered for the medical service of the Waffen-SS (Armed SS). There is little (and often contradictory) documentation about Mengele's activities between this time and early 1943. It is clear, however, that he first functioned as a medical expert for the Race and Settlement Main Office in summer 1940 at the Central Immigration Office North-East in Posen (today Poznan). He then served as a medical officer with the SS Division “Wiking” (SS Pioneer Battalion V), with which he saw action on the Eastern Front.
Mengele was born on 16 March 1911 to Walburga (née Hupfauer) and Karl Mengele in Günzburg, Bavaria, Germany. He was the oldest of three children; his two younger brothers were Karl Jr. and Alois. Their father was founder of the Karl Mengele & Sons company, producers of farm machinery. Josef was successful at school and developed an interest in music, art, and skiing. He completed high school in April 1930 and went on to study philosophy in Munich, where the headquarters of the Nazi Party were located. In 1931, Mengele joined the Stahlhelm, Bund der Frontsoldaten, a paramilitary organization that was absorbed into the Nazi Sturmabteilung (Storm Detachment; SA) in 1934.