Alphonse, whose wife Faydid of Uzes had either recently died or been repudiated, had sought to marry the now-adolescent Ermengardein 1142.

In reaction to this prospect, which would overturn the balance of power in the region by adding Narbonne to the direct control of Toulouse, a coalition of Occitan lords led by Roger II of Béziers, viscount of Carcassonne, Béziers, Albi and Razès, has formed an alliance against Toulouse.

In 1143, Ermengarde is married to a vassal of Roger II, Bernard of Anduze.

Alphonse is defeated by the coalition and taken prisoner, and is forced to make peace with Narbonne and restore Ermengarde and her new husband to the viscounty before being released.