Tupac next turned his attention to enlarging the southern limits of his empire. From Titicaca his armies advanced over hundreds of miles of bleak plateaux and barren deserts and down the steep Andean slopes into the fertile valleys of central Chile. His conquests extended as far south as the river Maule,--three hundred miles beyond Santiago,--but the tribes retained their autonomy and became rather allies than subjects. On the eastern side of the Andes he obtained the allegiance of the peoples living in the mountain valleys of north-western Argentine, and he completed the incorporation of the vast and fertile plateau which extends from the Titicacan basin to the present Argentine border. Returning to the northern frontier, he reduced the peoples who lived in the confused tangle of mountains and gorges which lies between the two Cordilleras north of Cerro de Pasco, thus extending his boundaries nearly to the present Ecuador line. The rest of northern Peru and all of southern Ecuador belonged to tribes who were loosely attached members of the confederacy headed by the Caras of Quito. They opposed only a short resistance to the arms and diplomacy of Tupac, and he made their territory the base for the great war which he proposed to undertake against the ancient kingdom of Quito. About the year 1455 he advanced with a great army, largely recruited from the tribes recently wrested from the Quito monarch, and defeated the Caras in a great battle. The whole plateau as far north as Riobamba submitted, reducing the Shiri's domain to the neighbourhood of Quito itself and a small region north of that city. However, all of Tupac's efforts to force the last barrier which interposed between him and the Cara capital failed, and he was compelled to content himself with extending his conquests on the coast as far as the Gulf of Guayaquil. In 1460 he returned to Cuzco, where three years later he was enraged to hear that the Shiri was making a desperate and partly successful effort to recover the lost provinces. Tupac's preparations for a final campaign to wipe the Quito kingdom out of existence were interrupted by his own death.