When Charles Gustav, De la Gardie's brother-in-law, ascended to the throne, it meant a return to the public for De la Gardie. In August 1654, he became governor of Västergötland, Dalsland and Halland and in December that year he was made chancellor of Uppsala University. In 1655, he was for the second time chosen for the office of General-Governor of Livonia. He also became Lieutenant General of the Swedish troops in Ingria, Estonia and Livonia, which meant that he commanded troops in the wars against the Polish-Lithuanian Commonwealth and Russia. It appears that De la Gardie was anything but a splendid military commander, as he received much more complaints than praise from the king for his actions in that area. During negotiations with Poland, De la Gardie was the prime Swedish representative. He took part in the deliberations leading to the Swedish-Polish Treaty of Oliva in 1660.