Following the Treaty of Roskilde (1658), he received his first civilian appointment, as Governor General of the newly annexed provinces of Schonen, Halland und Blekinge; acquired from Denmark.

In 1664, this led to another military appointment, as Lord High Admiral of Sweden, although he had never served in the Navy and had no seafaring experience.

[citation needed] During the Scanian War, the Swedish navy suffered devastating losses.

On 1 June 1658, he married the Gothenburg countess Christina Catharina De la Gardie [sv] (1632–1704); daughter of Field Marshal and Count Jakob De la Gardie (1583–1652) and Countess Ebba Brahe (1596–1674).

He also bought one of the largest estates in the Baltic area: Kolga manor [sv] in Kuusalu Parish, Estonia; from the De la Gardie family.