On the arrival of the Spaniards in 1566, a kind of desultory war was waged by them upon the various islands, in the hope of conquering them and extending their religion. In these wars they succeeded in gaining temporary possession of a part of Sooloo, and destroyed the tomb of Sayed Alli. The Spaniards always looked upon the conversion of the Moslems to the true Catholic faith with great interest; but in the year 1646, the sultan of Magindanao succeeded in making peace, by the terms of which the Spaniards withdrew from Sooloo, and were to receive from the sultan three cargoes of rice annually as a tribute. In 1608, the small-pox made fearful ravages, and most of the inhabitants fled from the scourge. Among these was the heir apparent, during whose absence the throne became vacant, and another was elected in his stead. This produced contention for a short time, which ended in the elected maintaining his place. This tribute continued to be paid until the flight of Amir to Basillan, about the year 1752, where he entered into a secret correspondence with the authorities at Samboangan, and after two years a vessel was sent from Manilla, which carried him to that capital, where he was treated as a prisoner of state. In June, 1759, an English ship, on board of which was Dalrymple, then in the service of the East India Company, arrived at Sooloo on a trading voyage. Dalrymple remained at Sooloo for three months, engaged in making sales and purchases. The Sultan Bantilan treated him with great kindness, and sought the interest of Dalrymple to obtain the liberation of his brother, who was now held prisoner by the Spaniards at Manilla, by telling him of his brother's wife, who had been left behind when Amir quitted the island, and had been delivered of twins, after he had been kidnapped by the Spaniards. Dalrymple entered into a pledge to restore Amir, and at the same time effected a commercial treaty between the East India Company and the Sooloo chiefs. By this it was stipulated that an annual cargo should be sent to Sooloo, and sold at one hundred per cent. profit, for which a return cargo should be provided for the China market, which should realize an equal profit there, after deducting all expenses. The overplus, if any, was to be carried to the credit of the Sooloos. This appears to have been the first attempt made by the English to secure a regular commercial intercourse with this archipelago. In the year 1760, a large fleet of Spanish vessels sailed from Manilla, with about two thousand men, having the Sultan Amir on board, to carry on a war against Sooloo.