Marinid state centred in today's Morocco to the south. Castile's objectives were to keep Granada in check, prevent it from conducting raids and force it to continue paying tribute. The tribute amount was 300,000 maravedís—about half of Granada's revenue—and represented an important source of income for Castile, though Granada often suspended payments. On the other hand, the Marinids, following in the footsteps of their Almohad and Almoravid predecessors, saw the protection of the Muslims in the Iberian peninsula, as well as participation in jihad against the Christian expansion there—the so-called "Reconquista"—as their duty as Muslims and as a way to increase their legitimacy. By the time of Muhammad II's rule, Granada's main objective was to maintain independence from both of these powers, preserve the balance of power, prevent an alliance between them, and control towns on the Castilian frontiers as well as ports on the Strait of Gibraltar, such as Algeciras, Tarifa, and Gibraltar. The contest over control of these strategically important ports, which controlled passage to and from North Africa, lasted until the mid-14th century, in what modern historians call the "Battle of the Strait" (Batalla del Estrecho). Besides these two foreign powers, Granada was also challenged by the Banu Ashqilula, another Arjona clan which was initially allied with the Nasrids, and whose military strength had helped establish the kingdom. They rebelled against Muhammad I from at least 1266, and received assistance from Castile, then under the rule of Alfonso X, who wanted to keep Granada in check. Alfonso sent a force under Nuño González de Lara to help the Banu Ashqilula, but the Castilian nobleman had his own grievances against Alfonso; Nuño González ended up rebelling against his king, and was welcomed by Muhammad I. In the beginning of Muhammad II's rule, the Banu Ashqilula's territories included Málaga—the second biggest city in the emirate after Granada and an important Mediterranean port—as well as Guadix. Accession and negotiation with Alfonso X On 22 January 1273, Muhammad I fell from a horse and died of his injuries. The younger Muhammad took the throne as Muhammad II. As he was the designated heir, the transition of power went smoothly. His first order of business was to deal with the Banu Ashqilula rebellion and the Castilian rebels who had been allied to his father and welcomed in Granadan territories. Relations with the Castilian rebels, who were led by Nuño González and had