When the Portuguese colonised part of Goa in the sixteenth century, they based their operations in the central district of Tiswadi, notably in the international emporium 'City of Goa', now Old Goa. As threats to their maritime supremacy increased, they built forts on various hillocks, especially along the coast. In 1624, they began to build their fortified town on the headland overlooking Mormugão harbour.The sultans of Bijapur, who had colonised Goa before the Portuguese, did not give up easily. There were several invasions. From the sea came the Dutch, who eventually took over from the Portuguese most of the coastal settlements: the Moluccas, Batticaloa, Trincomali, Galle, Malacca, Manar, Jaffna, Quilon, Cochin and Cannanore. From 1640 to 1643, the Dutch tried their best to capture Mormugão but were finally driven away.