[citation needed] He was one of the sovereigns who supported Britain in the American Revolutionary War with soldiers,[2] sending 1,228 men.

[3] His actions were opposed to the policy of the Holy Roman Emperor and to the moral sense of the age,[1] but he received a substantial monetary compensation.

[citation needed] Due to a quarrel with the Kingdom of Prussia, he was forced to flee into exile in Basel and later Luxembourg, where he died.

The dominion of Jever (which was annexed to Zerbst by the marriage of Prince Rudolph with Magdalene of Oldenburg, heiress of that land) was ruled under the Semi-Salic Law; for this, was given to the Empress Catherine II of Russia, born Princess Sophie Friederike Auguste of Anhalt-Zerbst and Frederick Augustus's only surviving sibling.

Her sister-in-law Princess Friederike Auguste Sophie of Anhalt-Bernburg ruled the territory of Jever as regent-governor on Catherine the Great's behalf until Napoleon's invasion in 1806.