[1] Under influence of his minister Hans Daniel Ludwig Friedrich Hassenpflug, he conducted a reactionary policy, which made him very unpopular.

His capital, Kassel, was occupied by Prussia, and, as a consequence of his refusal to negotiate,[1] he was transferred as a prisoner to Stettin on 23 June.

On 26 June 1831 Frederick William was morganatically married to Gertrude Falkenstein Lehmann (1803–1882).

She had been born in Bonn and was a daughter of apothecary Johann Gottfried Falkenstein and his wife, Magdalena Schulz.

When Frederick William met Gertrude, she was the wife of Lt Karl Michael Lehmann (married in 1822) and the mother of two sons.