He was at that time serving as a lieutenant in the Prussian life-guards at Potsdam.
After studying with distinction under the doctrinaires of Perigueux, he entered the life-guards of Louis XVI., and was present at Versailles on the memorable 5th and 6th of October 1789.
A captaincy in the Life Guards was given him, and in 1670, on the death of Monk, he was made captain-general of the king's forces.
Reinhold Fersen and entered the Swedish Life Guards in 1740, and from 1743 to 1748 was in the French service (Royal-Suedois), where he rose to the rank of brigadier.
For his services as commander of the cavalry regiment of the Life Guards on the occasion of the rebellion of 1825 he was created a count, and in the Turkish War of 1828-29 rose to the rank of lieutenant-general.
