At this period Cortez returned, after having surprised and vanquished Narvaez. By this action he acquired a great accession of force; and he is said to have had, after his arrival at the capital, one thousand infantry and one hundred horse. The siege was prosecuted with vigor and determination on the part of the natives, and the place defended with equal obstinacy and valor on the part of the Spaniards. Montezuma, who had ascended the terrace to address his subjects and to quell the insurrection, was killed by a stone or arrow, and his brother Quetlavaca proclaimed his successor. This gave renewed vigor to the Mexicans, and Cortez was compelled to retreat. His own account of his flight, in one of his letters, is well worth reading. The night of this disastrous retreat was called _La Noche triste_, the melancholy night. Cortez continued to retreat upon Tlascala, the Mexicans pursuing and harassing his rear. At Otumba, he was obliged to turn and give them battle. He describes his own troops as worn out with fatigue, but says that the enemy were so numerous that they could neither fight nor fly; and that the slaughter continued the whole day, until one of their principal chiefs was killed, which put an end to the battle and to the war. He reached Tlascala without further trouble, with the remnant of his forces, and was well received by his old allies. He was urged by his officers, and by the garrison of Vera Cruz, to retire to the coast, but refused to abandon the conquest of Mexico; and, in order to maintain the ascendency he had acquired over the people of Tlascala, he made incursions into the territories of the neighboring nations, whence he always returned victorious, and loaded with spoil. In December, 1521, he again marched upon Tenochtitlan, and took up his quarters in Tezcuco. From this place he carried on the war against the Mexicans and their allies, until the arrival of the frames of thirteen small vessels, which he had ordered to be constructed in Tlascala. They were brought by such a multitude of Indians, Cortez says, that “from the time the first began to enter the city until the last finished, more than six hours elapsed.” In order to launch these brigantines, as he calls them, a canal of half a mile in length was cut from the lake, of such ample dimensions, that eight thousand Indians worked every day at it, for fifty days, before it was completed.