On 31 August 1944, Monsabert took command of the French II Corps of General Jean de Lattre de Tassigny's Army B, later renamed the French First Army. Monsabert led the II Corps with distinction for the remainder of the war in Europe. Monsabert, with about 130000 soldiers took Toulon and Marseille and played an active part in Alsace with a corps numbering nearly 150000 soldiers at that time.