A pharmacist in the city of Carcassonne at the outbreak of the French Revolution, Frère exercised this profession until 1791, when he decided to join the army.

He was rapidly elected captain and took part to Pyrenees military operations against Spain during the War of the First Coalition.

[1] After the creation of the Grande Armée in 1805, Frère was given a command and was cited several times in the bulletins, during the War of the Third Coalition.

He was promoted to General of Division in March 1808, before being sent to Spain, where he took the city of Segovia on 7 June 1808 and then served as chief of staff in the Army Corps of Marshal Jean Lannes during the bloody siege of Saragosa.

In 1810, Frère was sent to serve in the Army of Catalonia and subsequently recalled to France and appointed at the command of the military division of Rennes.