[4] He fought for the first time defending the Tuileries Palace on the 10 August 1792 attack, as an officer of the Constitutional Guard of King Louis XVI.

Returning to his home province, he refused to comply with the levée en masse called by the outbreak of the French Revolutionary Wars and joined his cousin Louis Marie de Lescure on the latter's estates in Poitou.

At Fontenay he was famous for his contempt for danger, wearing three red handkerchiefs; on his head, around his neck and at his waist to defy the Republican gunners.

On 13 September the thumb of his right hand was shattered by a bullet during an engagement with Republicans at Martigné-Briand but he continued to fire at his opponents.

On 20 October, De la Rochejaquelein was unanimously elected as commander-in-chief of the Catholic and Royal Army, replacing D'Elbée who had been severely wounded in Cholet.

After this decisive rout, the Catholic and Royal Army was no longer a fighting force; De la Rochejacquelein had to take to the woods disguised as a peasant.