The rapidity with which a little band of Spaniards conquered the vast and warlike empire of the Incas is well-nigh incredible. The terror inspired by horses and firearms did much, but the capture of their emperor demoralised the imperial Inca tribes still more. Once in the possession of the sacred person of the monarch, the Spaniards were regarded by the Indians as his mouthpiece and the successor to his power. From Cuzco, the capital, a splendid system of roads and communications radiated to every part of the empire. The military and political dominance of the imperial tribes had weakened the power of resistance in the provinces. The elaborate structure which had been built up by the Incas rather facilitated than hindered the Spanish conquest, once the decisive blow had been given at the centre. The provinces submitted to the new rulers as fast as the Spanish columns could march over the magnificent mountain roads. South from Cuzco the Inca empire extended 2000 miles. It covered the whole Andean region as far as the 37th degree of south latitude and extended from the Pacific to the eastern slopes of the Andean foothills. In the present Argentine it included the tribes living in the lesser chains which occupy the north-western part of the republic. Some of these Argentine tribes seem to have been only tributary to the Incas, others were completely dependent, and extensive colonies had been founded in the cotton regions. The general language was Inca, and that admirable system of irrigation and intensive culture which made Peru proper a garden had been introduced on the eastern slopes of the southern Andes. The southern part of the great Bolivian plateau seems to have submitted quietly to the Spanish conquerors, and the stream of adventurers passed on to the south. In 1542, Diego de Rojas led the first expedition, of which a record has survived, down through the Humahuaca valley into the actual territory of the Argentine. He himself perished in a fight with a wild tribe near the main chain of the Andes, but his followers continued their march. Near Tucuman, they passed out from the mountain defiles unto the pampa, and, leaving the desert to their right penetrated through Santiago and Cordoba, to the Parana.