Subsequently, he participated in all the campaigns in Flanders directed by Philippe le Bel and his son Louis X (in 1303, 1304, 1313 and 1315).

This military activity was very expensive and impoverished Bernard VI and he was obliged to borrow 2500 gold florins for the funeral of his wife.

After the death of Gaston VII, Viscount of Béarn, his grandfather, he maintained a long war against the Counts of Foix following the controversy over the will.

The conflict escalated into an undeclared war between the houses of Foix and Armagnac, which took place during nearly all of the fourteenth century.

He first married Isabella d'Albret (c. 1275 † 1 December 1294), daughter of Bernard Ezy IV Sire of Albret and Jeanne de Lusignan.