Rewarded with the earldom of Fogelvik, he belonged to the cautious senior officers, who he hesitated when faced with Charles XII's aggressive plans, and allied with his son-in-law Arvid Horn in opposition to the King.

[1][2][3][4][5] When the Scanian war began in 1675, Gyllenstierna was recalled by the Swedish government; becoming colonel of Norra Skanska kavalleriregementet in 1677.

At the outbreak of the Great Northern War, Gyllenstierna who was commander-in-chief of the Swedish forces in Germany, crossed the Elbe, and beat the Danes at Reinbek.

In 1708, he commanded the forces of the Lower Saxon Circle that occupied Hamburg, and was rewarded for the successful operation with promotion to field-marshal.

After the battle of Poltava, Gyllenstierna opposed the rearmament policy advocated by Magnus Stenbock, as too onerous for the country, and in the Royal Council he joined with his son-in-law Arvid Horn in his opposition to the absent King.