In Piedmont, meanwhile, a stalemate had developed between the French, under the Sieur de Boutières, and the Imperial army, under Alfonso d'Avalos; d'Avalos had captured the fortress of Carignano, and the French had besieged it, hoping to force the Imperial army into a decisive battle. During the winter of 1543–44, Francis significantly reinforced his army, placing Enghien in command. D'Avalos, also heavily reinforced, advanced to relieve Carignano; and, on 11 April 1544, Enghien and d'Avalos fought one of the few pitched battles of the period at Ceresole. Although the French were victorious, the impending invasion of France itself by Charles and Henry forced Francis to recall much of his army from Piedmont, leaving Enghien without the troops he needed to take Milan. D'Avalos's victory over an Italian mercenary army in French service at the Battle of Serravalle in early June 1544 brought significant campaigning in Italy to an end.