Desaix was born to a noble family in the Château d'Ayat in Ayat-sur-Sioule, in the province of Auvergne, to Gilbert des Aix, Lord of Veygoux, the family manor in Charbonnières-les-Varennes, and Amable de Beaufranchet, his wife and first cousin. Desaix received his military education at the school founded by Marshal d'Effiat, and entered the French royal army. During his first six years of service, he devoted himself to duty and to military studies. When the French Revolution broke out, he threw himself into the cause of liberty. Refusing to "emigrate", he joined the staff of Charles Louis Victor de Broglie, prince de Broglie the Jacobin son of prince de Broglie. This nearly cost Desaix his life, but he escaped the guillotine, and by his conspicuous service soon came into favor with the Republican government. Like many other members of the old ruling classes who had accepted the new order, the instinct of command joined to native ability, brought Desaix career success, and thus he had attained the command of a division in 1794.