[4][5] Stackelberg began his military career in 1685 and later participated in the Nine Years' War on both sides, first in service with the Dutch from 1688 to 1690 and then with the French until 1696.

[7] In 1704, Stackelberg was transferred to the army of Adam Ludwig Lewenhaupt and was present at the battle of Jakobstadt and the capture of Biržai Castle.

[2] In 1708, after Charles XII began his campaign in Russia, Lewenhaupt was tasked with carrying supplies for the King's army.

[10] After meeting up with Charles’ army, Stackelberg then came under the direct command of the king himself and would lead a Swedish detachment across the river Desna as well as repulse a subsequent Russian counterattack.

[11] Stackelberg was taken prisoner along with many other generals after the battle and was forced to take part in Tsar Peter the Great's victory parade in Moscow.

After returning to Sweden, Stackelberg was promoted to general and given command of the Åbo County Infantry Regiment [sv].