Born on 16 May 1771 in Damvillers, France in what later became the department of Meuse, Loison briefly enlisted in a colonial battalion on 29 June 1787. However, he left the unit in September and when he returned on 25 January 1788, he was immediately granted leave. After the outbreak of the French Revolution, his father served as a Deputy in the Constituent Assembly. He was appointed sous-lieutenant in the "Meuse" Volunteer Battalion on 15 September 1791 and became lieutenant in 1792. Several months later, he emerged as captain of hussars in the "Légion du Nord". In May 1793, the Representative-on-mission of the Army of the North (France) promoted him to adjutant general (a rank equivalent to colonel) for bravery. This appointment was later confirmed. On 16 October 1793 at the Battle of Wattignies, he accompanied the 3,500-man column of Jacob Job Élie on the far right flank of the army. In the middle of the night, the outposts were attacked by the Austrians and the untried foot soldiers took to their heels. Élie managed to rally his men but Johann Andreas Benjowski's Austrians launched an assault in a heavy fog at dawn. The second line panicked and fired into the backs of the first line, whereupon the infantry bolted again, throwing away their muskets in order to run faster. They might have been butchered but for Loison who led the cavalry to the rescue and fought off the pursuit. French losses were 400 soldiers and 12 artillery pieces while the Austrians lost 138 men in the clash.