But the marriage soon turned to scandal, when, shortly after, Alfonso XI dispatched Mary to a convent and took up openly with his mistress, Leonor Núnez de Guzmán.

The Genoese captain Emanuele Pessagno (Manuel Pessanha) had been hired by King Denis of Portugal in 1314 to develop a permanent navy.

But simultaneously, a Castilian fleet of 40 galleys sailed out of Seville, under the Galician captain Alfonso Jofre Tenório (Señor de Mogue), probably intending a similar landing on the Portuguese coast.

With the wind in their favor, the Portuguese gained the initial advantage and managed to seize as many as 9 Castilian galleys early in the encounter.

The final peace and reconciliation between Afonso IV and his son-in-law Alfonso XI was effected only two years later, with the Treaty of Seville in July 1339, mediated by Maria of Portugal.

Among the treaty's provisions was a commitment by Afonso IV of Portugal to assist Alfonso XI of Castile against an impending Marinid invasion force, then assembling in Morocco.