Aissó is thought to have been either a Goth and former lieutenant of the disposed Count Berà, or an Arab (Ayxun ibn Sulayman ibn Yaqdhan al-Arabí), the son of Sulayman al-Arabi who had been imprisoned in Aachen after being captured by Frankish forces at Girona.
Many Goth nobles joined Aissó and Guillemó (or Guillemundus) son of Berà and Count of Rasez and Conflent.
The young Count Bernat requested and received some help from the Emperor, as well as from some local Goth noblemen or "Hispani" (826).
Faced with this opposition, Aissó appealed to the sole power that could be compared to the Franks, the Emir of Córdoba.
When Louis I the Pious heard of the Muslim raid, he ordered to his son Pepin I of Aquitaine, and Counts Hugo of Tours and Matfred of Orleans to recruit an army.