When the hereditary prince of Hesse-Cassel, the later Frederick II, converted to Roman Catholicism, his father, the reigning landgrave William VIII decided to do what he could to limit his son's future realm.

[1][2] As count William was underage, his mother the landgravine, princess Mary of Great Britain, ruled as his legal guardian.

[3] Until then Hesse-Hanau was ruled as an independent state, undergoing extensive modernizations with the erection of significant buildings in the capital of Hanau.

[4] Means for this came from the subsidies the reigning count received from his uncle, king George III of Great Britain.

In return, Hesse-Hanau made available a contingent of 2,400 soldiers for the use of the British Crown in the American Revolutionary War.