Born on 8 November 1754 to parents Balthazar D'Allemagne (1710–1772) and Marie Lasalle (1731–1799), Claude D'Allemagne grew up in Peyrieu, Ain, France. A year after his father died, he enrolled in the Hainaut Regiment, taking Dallemagne as his new surname. In 1777, his battalion embarked for the West Indies with Comte d'Estaing's fleet. He fought in actions at Dominica, St. Vincent, Grenada, and St. Lucia, being wounded in the latter combat. In 1779 he took part in the ill-fated Siege of Savannah in Georgia. By 1786, he earned advancement to sergeant-major.