The son of Yahuar-huaccac assumed the name of the Deity, and called himself Uira-cocha.[1172] Intervening in a war between the two principal chiefs of the Collas, named Cari and Zapaña, Uira-cocha defeated them in detail, and annexed the whole basin of Lake Titicaca to his dominions. He also conquered the lovely valley of Yucay, on the lower course of the Vilcamayu, whither he retired to end his days. The eldest son of Uira-cocha, named Urco, was incompetent or unworthy, and was either obliged to abdicate[1173] in favor of his brother Yupanqui, the favorite hero of Inca history, or was slain.[1174] It was a moment when the rising empire needed the services of her ablest sons. She was about to engage in a death-struggle with a neighbor as powerful and as civilized as herself. The kingdom of the Chancas, commencing on the banks of the Apurimac, extended far to the east and north, including many of the richest valleys of the Andes. Their warlike king, Uscavilca, had already subdued the Quichuas, who dwelt in the upper valleys of the Apurimac tributaries to the southward, and was advancing on Cuzco, when Yupanqui pushed aside the imbecile Urco, and seized the helm. The fate of the Incas was hanging on a thread. The story is one of thrilling interest as told in the pages of Betanzos, but all authorities dwell more or less on this famous Chanca war. The decisive battle was fought outside the Huaca-puncu, the sacred gate of Cuzco. The result was long doubtful. Suddenly, as the shades of evening were closing over the Yahuar-pampa,—“the field of blood,”—a fresh army fell upon the right flank of the Chanca host, and the Incas won a great victory. So unexpected was this onslaught that the very stones on the mountain sides were believed to have been turned into men. It was the armed array of the insurgent Quichuas who had come by forced marches to the help of their old masters. The memory of this great struggle was fresh in men’s minds when the Spaniards arrived, and as the new conquerors passed over the battlefield, on their way to Cuzco, they saw the stuffed skins of the vanquished Chancas set up as memorials by the roadside. [Illustration: WARRIORS OF THE INCA PERIOD. [After a cut given by Ruge, and showing figures from an old Peruvian painting.—ED.]] The subjugation of the Chancas, with their allies the Huancas, led to a vast extension of the Inca empire, which now reached to the shores of the Pacific; and the last years of Yupanqui were passed in the conquest of the alien coast nation, ruled over by a sovereign known as the Chimu. Thus the reign of the Inca Yupanqui marks a great epoch. He beat down all rivals, and converted the Cuzco kingdom into a vast empire. He received the name of Pachacutec, or “he who changes the world,” a name which, according to Montesinos, had on eight previous occasions been conferred upon sovereigns of the more ancient dynasties.