In view of the French defeats in northern Italy, MacDonald was instructed to garrison central and southern Italy and come north by forced marches with the "Army of Naples". The order arrived on 14 April 1799 and MacDonald began his move north on 7 May. MacDonald named Salme to lead the 2,997-man army Advance Guard which was made up of the 15th Light (1,390 men) and 11th Line (1,440 men) Infantry Demi-brigades, 94 troopers from the 25th Chasseurs à Cheval and 53 gunners and sappers. At 8:00 am on 17 June 1799, MacDonald opened the Battle of Trebbia by sending 18,700 soldiers from the divisions of Claude Perrin Victor, Jean-Baptiste Dominique Rusca and Jean Henri Dombrowski plus Salme's Advance Guard into action. At first the French pressed back the Austrians of Peter Karl Ott von Bátorkéz but reinforcements began to arrive until the Coalition commander Alexander Suvorov had 30,656 Austrians and Russians on the field. MacDonald had been wounded at the Battle of Modena and delegated Victor to direct the assault. But Victor never took charge of the troops that day and the French fought without a guiding hand. Late in the day, Salme's Advance Guard covered the retreat of the three French divisions behind the Tidone River.