In World War I, he served as a Feldrabbiner (Jewish chaplain) in the German army, primarily on the Eastern front.

Aron Tänzer received his doctorate in 1895 and in October 1896 he successfully applied for the vacant rabbinical position in Hohenems, Austria.

The Hohenems rabbinate also supervised nearby Jewish communities in Vorarlberg and, from 1878 to 1914, also formally the Jews living in Tyrol.

Tänzer applied his extensive training in history to numerous scientific publications as well as the field of adult education.

Tänzer looked after the soldiers, helped in the hospital and set up people's kitchens for the needy population.