Finally in February 1739, Chimaji Appa invaded Bassein Fort. He first occupied Versova fort., Dharavi and blockaded Bassein Creek. Then mines were laid at various points under the fort walls and detonated, causing a breach in the wall. As the Marathas including Ranojirao Shinde and his cousin grandfather Janojirao son of Shrimanat Changojirao poured into the fortress, the Portuguese fought on desperately and viciously, using their technically advanced weapons and artillery, they caused high casualties among the Marathas. Inch by inch the fort was secured and resistance contained in small pockets. At this stage the tower of Saint Sebastian collapsed in an explosion, and Portuguese morale plummeted.