Portuguese-era masonry in Mannar Fort: coral rag bonding and round bastions vs Dutch squares?

Mannar Fort reveals a clear stratigraphic evolution of colonial military engineering. Originally constructed by the Portuguese in 1560, the early defenses utilized circular or curved corner bastions engineered to deflect medieval cannon shot. When the Dutch VOC captured the fort in 1658, they demolished curved works and rebuilt the perimeter according to Coehoorn trace principles. They erected four angular pointed square bastions built of dressed Miocene limestone and fossilized coral blocks. The Dutch bastions provided interlocking defensive fire corridors that eliminated blind spots along the dry moat.