On July 15 the Turks delivered a grand assault by sea and by land. The attack by sea, under the command of the renegade Candellissa, proved the more formidable. At the critical moment the defenders were thrown into confusion by an explosion on the ramparts, during which the Turks were able to make their way through the stockade and into the fortress, being checked with difficulty by the desperate resistance of the garrison and finally driven out by a timely reinforcement sent by La Valette. Ten boatloads of troops sent by Mustapha incautiously exposed themselves to the guns of St. Angelo and were almost all sunk, while the attack on the land side, led by Hassan, Viceroy of Algiers and son of Khaired-Din Barbarossa, proved an utter failure. As at the siege of Rhodes, so at Malta, a distinct part of the fortifications had been allotted to each langue to defend. The langue of Castile held the north-east section of Il Borgo, which was destined to be the scene of most desperate fighting. On August 7 a joint attack was made on the land side of Senglea and on the bastion of Castile. On that day the Turks came nearer success than ever before or after. Mustapha's desperate attacks on Senglea were at last successful: masters of the breach made by their guns, the assailants' weight of numbers began to tell, and slowly the defenders were being pushed back inside the fortress. At this moment, to everyone's amazement, Mustapha sounded the retreat. The little garrison of the Città Notabile, which had been left alone by the Turks, had been raiding the enemy's lines as usual, and, hearing the grand assault was in progress, had made a determined attack on the Turkish entrenchments from behind, burning and slaying all they could find. The confusion arising from this started the rumour that Sicilian reinforcements had landed and were attacking the Turkish army. Mustapha, in fear of being surrounded, drew off his troops in the moment of victory. Meanwhile,[3] farther north, the Bastion of Castile had been almost captured by Piali. The rock at that part of the fortification was extremely hard, and the possibility of mines had occurred to none of the garrison. Piali, however, with great labour, had dug a mine which had been sprung that morning and had blown a huge gap in the ramparts. This unexpected attack threw the whole of Il Borgo into confusion, and, but for the Grand Master's promptitude and coolness of mind, the enemy had been masters of the fortress. Seizing a pike, La Valette rushed into the fight, and, inspired by his example, the Knights succeeded in driving the enemy out of the breach. He ordered the garrison to remain there all night, as he expected an attack under the cover of darkness, and insisted on taking the command himself. His subordinates protested against this reckless exposure of a valuable life, but his precautions were justified when a Turkish attack made in the darkness was defeated by his prompt resistance.