During the year 1551 Valdivia occupied himself in fortifying Concepcion and making preparations for an invasion of Araucania. Heavy reinforcements came and he advanced encountering at first no serious opposition. He founded the city of Imperial, one hundred and fifty miles south of Concepcion, and thence pushed a hundred miles farther on, where he established a seaport, calling it by his own name. Returning north in 1553, on his way he built several forts in the Araucanian territory, and at Santiago found a fresh body of troops, and, what was even more important, a supply of horses. Two hundred men were despatched across the Andes to begin the conquest of what is now known as the province of Mendoza in the Argentine Republic. Fancying that he had practically completed the subjection of Chile, Valdivia sent a messenger to Spain to sue for the title of Marquis and a perpetual governorship, and fitted out an exploring expedition to the Straits of Magellan in the vain hope of opening up direct sea communication with the mother country. The Araucanians had, however, not relaxed their determination to rid themselves of the white invaders. News came that the confederacy had put an army of ten thousand men in the field, and that the outlying forts had been stormed. Valdivia at once advanced from Concepcion at the head of his forces, numbering two hundred Spaniards and five thousand Indian auxiliaries. A hundred miles south of the city he came in sight of the Araucanian army. For some time the Indian commander manoeuvred cautiously, endeavouring to draw the Spaniards into a position where he could charge without suffering too much from the dreaded artillery. Finally battle was joined, and despite the destructive fire the Indians managed to come to close quarters. As soon as these fierce warriors reached the enemy's line all was up with the invaders. The Spanish army was literally annihilated. Valdivia himself fled, but was pursued and quickly captured. Brought before the Indian general he begged for his life, agreeing to quit Chile with all the Spaniards, but his protestations were cut short by the war club of an old chief standing near.