He and the Prince fought as part of a vast cavalry force at the Surprise of Meaux on 28 September 1567. de La Rochefoucauld also fought at the Siege of Chartres and raised a huge army to save the prince de Condé at La Rochelle, before accompanying him to Languedoc to join forces with Jacques II de Crussol's forces. On 13 March 1569 he fought at the Battle of Jarnac, in which the prince de Condé was killed. He then fought under Henry of Navarre, the prince's paternal nephew, at La Roche-l'Abeille. He also took part in the assaults on Beaugency and Pons and the sieges of Nontron, Lusignan and Poitiers in summer 1569 before coming to the assistance of Châtellerault and fighting at Port-de-Piles and on 3 October 1569 at Moncontour.