On 30 September 1831, he became co-regent and, in 1847, Prince-elector. Under influence of his minister
Hans Daniel Ludwig Friedrich Hassenpflug, he conducted a reactionary policy, which made him very unpopular. He was forced to give in to the demands of the
March Revolution, but reinstated Hassenpflug in 1850 after the revolution had been crushed. In the
Austro-Prussian War of 1866, he chose the side of Austria. His capital,
Kassel, was occupied by Prussia, and, as a consequence of his refusal to negotiate, he was transferred as a prisoner to
Stettin on 23 June. Hessen-Kassel was annexed by Prussia in the same year. Frederick William never accepted the Prussian dominance over his territory. Even after the creation of the unified
German Empire in 1871, he tried to regain his throne. == Personal life ==