In 1733 he joined the regular army as a volunteer engineer and on May 1, 1734 was appointed a second lieutenant in the Regiment de Bearn.
In the War of the Austrian Succession his engineering service won distinction and he received the Cross of the Order of St. Louis and in September, 1748 a Captain's commission.
In July and August, 1756 he assisting in laying out the siege works in the Battle of Fort Oswego.
In July 1759 a joint British and Iroquois force commanded by General John Prideaux and William Johnson laid siege to Fort Niagara.
After a relief force from Fort Machault under the command of Captain François-Marie Le Marchand de Lignery was routed by the besiegers at La Belle Famille on 25 July, Pouchot was obliged to surrender the fort to Johnson.