He did play an important rôle, when he acted as mediator and representative of the French Cardinal Mazarin in the imperial election of 1658 and the negotiations that led to the formation of the Rhenish Alliance, also in 1658.

The military struggle for control of Borculo ended with the intervention of France and Brandenburg, to the detriment of von Galen.

In an attempt to compensate for this financial disaster, Frederick Casimir was considering mortgaging the county of Hanau-Lichtenberg to the Duke of Lorraine and to convert to Roman Catholicism, in the hope of securing support from that side.

George Christian then attempted to purchase the district of Dorheim, including the salt mine of Nauheim, which was very important for the economy of Hanau.

In an attempt to sideline Frederick Casimir's relatives, who were opposed to selling off large parts of the county, George Christian tried to become regent of Hanau.

After lengthy negotiations, Emperor Leopold I decided that Count Palatine Christian II of Zweibrücken-Birkenfeld and his sister Countess Palatine Anna Magdalena of Birkenfeld-Bischweiler, the guardians of Frederick Casimir's nephews and successors were appointed co-regent of Hanau, with the right to veto the decisions of the Count.

On 11 October 1666 in Hamburg, George Christian married Anna Catharina of Pogwitsch (1638-1694), the widow Count Frederick of Ahlefeldt (1618-1665).