A series of military actions and diplomatic moves were undertaken in 1635 and 1636 by the Dutch East India Company (VOC) in Dutch-era Taiwan (Formosa) aimed at subduing hostile aboriginal villages in the southwestern region of the island. Prior to the campaign the Dutch had been in Formosa for eleven years, but did not control much of the island beyond their principal fortress at Tayouan, and an alliance with the town of Sinkan. The other aboriginal villages in the area conducted numerous attacks on the Dutch and their allies, with the chief belligerents being the village of Mattau, whose inhabitants in 1629 ambushed and slaughtered a group of sixty Dutch soldiers.