[1] After the death of her younger brother Matthew in 1398, who had tried to claim the Aragonese crown for his wife Joanna, Isabella was the last living member of the House of Foix and was heir of a large ownership which focused especially on the northern slopes of the Pyrenees.

This heritage was to be denied to Isabella by the French Crown because of her marriage to Archambaud, whose family had been supporters of the English during the Hundred Years' War.

The Treaty of Tarbes on 10 May 1399 saw Isabella made countess as long as her husband stopped his alliance with the English and allow the two oldest sons of the couple to be taken to royal court.

The loyalty of the new dynasty of Foix to France was awarded in 1412, when Archambaud was appointed lieutenant-general of the Languedoc.

However, in 1413, Joan died leaving no issue and John a widower, all hope of a union had now failed.