Adolphus was made honorary Colonel-in-Chief of the Hanoverian Guard Foot Regiment 1789–1803, but his military training began in 1791, when he and Prince Ernest went to Hanover to study under the supervision of the Hanoverian commander Field Marshal Wilhelm von Freytag. He remained on Freytag's staff during the Flanders Campaign in 1793. His first taste of action was at Famars on 23 May. He was wounded and captured at the Battle of Hondschoote 6 September, but was quickly rescued. As a Hanoverian General-Major, he commanded a Hessian brigade under his paternal great-uncle, General Johann Ludwig von Wallmoden-Gimborn in Autumn 1794, then commanded the Hanoverian Guards during the retreat through Holland. Remaining in Germany, he commanded a brigade of the Corps of Observation from 22 October 1796 until 12 January 1798. He was made a British Army colonel in 1794, and lieutenant general on 24 August 1798. In 1800 – whilst stationed in the Electorate of Hanover – he attended the founding of a village (part of the settlement of the moorlands north of Bremen), which was named after him: Adolphsdorf (since 1974 a component locality of Grasberg).