Abu-l-Walid was an implacable foe of the Christians. His assault on Gibraltar was frustrated; but he gained a signal victory over the Castilians in 1319, when the princes Pedro and Juan were killed. Following up this success, he marched upon the towns of Martos and Baza, and ravaged the country. It was at the latter town that artillery was first used in Spain. Hailed with joy, the victorious Abu-l-Walid returned to Granada bearing the spoils of war. Among the captives was a maiden of unusual beauty, whom he had wrested from an inferior officer. This act so incensed the chieftain that three days after he stabbed his ruler outside the Alhambra. Dying from the wound, Abu-l-Walid exacted an oath of fealty from the eminent and powerful to his eldest son, Mulai Mohammed Ben Ismaïl. This command was fulfilled before the sultan's minister disclosed the death of his royal master. The boy king, Mohammed IV., was soon busy quelling factions in his State, and repelling the African army, which took in turn Marbella, Algeciras, and Ronda. He also defeated the Castilians in several desperate encounters, but lost the day at Gibraltar. [Illustration: GRANADA--IN THE MARKET] Mohammed IV., who was assassinated at Gibraltar by his allies the Moroccans, was succeeded in 1333 by his brother Yusuf I. This king was a hater of warfare; he sought the peaceful reform of the community rather than the expansion of his kingdom. Under his rule Granada prospered and the condition of the people was bettered. Yusuf I. was disturbed in the tranquillity of his noble palace at Malaga by the appeals of the African potentates for his aid in reconquering Spain. Compelled to join the invaders, he sustained a severe disaster at the Salado, and was forced to acquire peace at the cost of yielding Algeciras. He was murdered by a madman in 1358. Mohammed V. was the next sovereign. He was a worthy son of his high-principled father, Yusuf; but fate decreed that his reign should not prove peaceful, for soon after his accession, his younger brother Ismaïl conspired with certain officers of state and made an attempt to gain the throne. Upon a night in August, 1360, about one hundred conspirators climbed the walls of the Kasba and after killing the wizir, proclaimed Ismaïl as sultan. Mohammed, who was without the palace at the time, essayed to enter; but he was received with a flight of arrows, and mounting a horse he galloped away to Guadix. Here he was welcomed, and from this town he sped to Marbella, thence to Africa, where he received the aid of Abu-l-Hasan. With troops lent to him he returned to Spain, hoping to crush the usurper. But Abu-l-Hasan capriciously ordered the return of his soldiers, and Mohammed retreated to Ronda with a few adherents. Dissension had arisen meanwhile between Ismaïl and Abu Saïd, one of the chief conspirators, who was burning to take the reins of government in his own hands. Ismaïl was besieged by Abu Saïd, and upon venturing out of his palace was slain.