As a result of the Treaty of Tarbes signed on 10 May 1399, John's parents were given possession of the County of Foix, but it required that his father renounce his English alliance, and it stipulated that John and one of his brothers were to be sent as hostages to the Royal Court of France to ensure observance of the terms of the treaty.
On 24 April 1406 Charles VI of France recognised John as heir to the County of Foix and he was also involved in several operations against the English: the Siege of Bordeaux in 1404-1405 and the Seat of Blaye in 1406.
In 1409, John accompanied King Martin of Aragon on an expedition to Sardinia against the Genoese at the Battle of Sanluri on 30 May 1409 and returned to Foix in September.
The dowager Queen Violant of Aragon, widow of King John I, wrote to John on 20 January 1411 promising the return of Rosanes and Martorell (part of the properties confiscated from his maternal uncle Matthew of Foix) if her daughter Yolande succeeded to the throne, as a result John sent troops to help Louis and Yolande in their claim, but Ferdinand prevailed ultimately on 25 June 1412 by the compromise of Caspe.
However, John was able to gain the lost estates by a marriage to Joanna of Urgell, granddaughter of Peter IV of Aragon.