At only nine years of age, he accompanied his father on his military duties for the Prussian army.

In 1733 he led the Prussian forces stationed in the city of Mühlhausen in Thuringia during the First Silesian War.

The death in 1737 of his elder brother, the Hereditary Prince William Gustav, made Leopold the new heir of Dessau.

The late prince was already married and had nine children, but his wife was of non-noble birth; for this reason, the issue of the marriage was barred from succession.

In 1752 Frederick the Great named a newly founded village Leopoldshagen (est.