He sailed with Admiral Charles Henri Hector, Count of Estaing during the American Revolutionary War and was wounded at the Siege of Savannah in autumn 1779.

[3] After King Louis XVI's Flight to Varennes in June 1791, large numbers of noble officers began leaving the Royal Army.

[9] On the night of 16–17 December, Dugommier ordered an assault on Fort Mulgrave which was defended by 5,000 Spanish and 700 British troops.

[12] Historian Ramsay Weston Phipps described La Barre as, "An ex-noble, he had made himself popular, although maintaining discipline, and was a fine leader".

Dugommier opened the Second Battle of Boulou by threatening the Spanish left, then threw the main weight of his attack into the gap.

La Barre led the two regiments across to the south bank at the Saint-Jean ford and raced for the Céret bridge which his horsemen seized.

[15] After Boulou, Dugommier carried out the Siege of Collioure using the divisions of La Barre and Pierre François Sauret.

[16] At the same time, the French also besieged the Fort de Bellegarde which held out until its Spanish garrison finally capitulated on 17 September.

[16] On 6 May, Charles-Pierre Augereau disregarded his orders and led his right wing division to occupy Sant Llorenç de la Muga where there was a Spanish cannon foundry.

Occupied with the sieges of both Collioure and Bellegarde, Dugommier wanted his division commander to withdraw to a less exposed position, but Augereau obstinately refused.

On 19 May 1794, 15,000 Spanish troops attacked Augereau's 6,000 men in the First Battle of Sant Lorenç de la Muga.

When Dugommier assumed command, two new representatives were assigned to the army, Pierre Soubrany and Édouard Jean Baptiste Milhaud.

[20] At La Jonquera, Dugommier ordered Catherine-Dominique de Pérignon, leading his center division, to mount a reconnaissance of the Spanish defenses and try to interfere with their construction.

On the night of 6 June, Pérignon advanced on the Spanish positions, crossing to the west bank of the Llobregat River.

The French horsemen were routed by the superior force of Spanish cavalry and La Barre was mortally wounded.