The German Luftwaffe (Air Force), Heer (Army), Kriegsmarine (Navy) and the Waffen-SS used Arabic numerals as well as Roman numerals to distinguish between the different units, sub-units and organization levels of their respective military branch.
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Luftwaffe flying units
Units of the Heer or Waffen-SS
The Heer or Waffen-SS used a similar naming convention to the Luftwaffe. An Infantry, Panzer, Grenadier division was normally composed of three regiments. Each of these regiments was composed of three battalions denoted by Roman numerals. Each battalion was composed of three companies which were numbered by Arabic numerals. This naming scheme also applied to land based units of the Kriegsmarine, Luftwaffe and the Waffen-SS.
References
Nomenclature used by the Wehrmacht and Waffen-SS Wikipedia(Text) CC BY-SA