His army service began in 1792 during the French Revolution when he enlisted in a cavalry regiment as a trooper.

During the French Revolutionary Wars he advanced through the ranks and became commander of a light cavalry regiment in 1802.

Believing he was about to be replaced, Bernadotte wrote a letter to Bonaparte asking that he find employment for his aides Maurin and Eugène-Casimir Villatte.

[2] On 24 April 1802 Maurin was named to lead the 24th Chasseur à Cheval Regiment as Chef de Brigade (colonel).

[3] While still a colonel, he led a brigade consisting of the 15th and 24th Chasseurs à Cheval at the Battle of Caldiero on 29–31 October 1805.

[3] He reported to François Étienne de Kellermann who commanded a cavalry division that included one squadron each of the 26th Chasseurs à Cheval, 1st, 3rd, 4th, 5th, 9th, and 15th Dragoons.

He and 70 other French soldiers were captured by Portuguese partisans on 16 June 1808 and handed over to the captain of a British naval vessel as prisoners.

[9] An order of battle for 10 March notes that the division included a detachment from the 5th Horse Artillery armed with three 6-pounder guns and one howitzer, numbering 53 gunners and 53 teamsters.

The division's 1st Brigade was led by Louis Vallin and consisted of the 6th Hussars and 8th Chasseurs à Cheval Regiments.