In 1354, Louis I, Duke of Anjou was appointed as the Governor of Tourraine and Jean de la Jaille joined his service. In 1355, Jean was in the entourage of Jean de Clermont, Maréchal de France and Lieutenant General to the King in Touraine and Poitou, one of the most powerful and brilliant Barons in the Court of Jean le Bon. He was fortunate to escape with his life at the Battle of Poitiers in 1356. Jean de la Jaille remained in the service of Louis I of Anjou, and was nominated Captain and Defender of Loudun in 1360, a function he fulfilled with honour and success for over 30 years.