It was formed in 1657 during the Ancien Régime as the régiment Mazarin-Catalans, being renamed the régiment Royal Catalan in 1661 then the régiment Royal Roussillon in 1667. Its first battalion fought in the French and Indian War from 1756 to 1761 in Canada under the command of général Louis-Joseph de Saint-Veran, Marquis de Montcalm, with M. de Sennezergue as its colonel. It fought at the Battle of Fort William Henry and at the Battle of the Plains of Abraham – at the latter it was broken and forced to flee by steady fire from the British 35th Foot, whose members are traditionally held to have picked up the 54th's plumes and placed them in their own headdress (the Roussillon Plume being formally incorporated into the badge of the 35th Foot in 1881). A second battalion of the Royal Roussillon served in Germany (1756–1762). In 1756, the 54th Infantry Regiment's uniform was white with blue facings, five gilded buttons for the linings and 3 buttons on each pocket.