The sultans of Tidore ruled most of southern Halmahera, and, at times, controlled Buru, East Ceram and many of the islands off the coast of New Guinea. Tidore established an alliance with the Spanish in the sixteenth century, and Spain had several forts on the island. There was mutual distrust between the Tidorese and the Spaniards but for the Tidorese the Spanish presence was helpful in resisting the incursions of the Ternateans and their ally, the Dutch, who had a fort on Ternate. For the Spanish, backing the Tidore state helped check the expansion of Dutch power that threatened their nearby Asia-Pacific interests, provided a useful base right next to the centre of Dutch power in the region and was a source of spices for trade.