In 1796, he joined the Prussian army. Before his retirement from active service, Henry was elevated to the rank of Generalmajor. Henry reassumed his rulership over Pless until his death.
The union was childless.
Since his youth, Henry was a strong advocate of homeopathy. In 1821 he took under his protection its creator, Samuel Hahnemann, who remained with his large family in Köthen for the next fourteen years as Henry"s personal physician.
From 1841, he resumed service in the Prussian army, and by the time of his death, he was a General of Infantry. With him, the line of Anhalt-Köthen became extinct.
On his death, the duchy was inherited by his kinsmen Alexander Karl of Anhalt-Bernburg and Leopold IV of Anhalt-Dessau, however Alexander renounced his rights over Köthen on behalf of Leopold IV, since it was clear that his eventual assumption of all the Anhalt lands was inevitable.