After Shivaji successfully constructed Khanderi, great naval battle between Maratha & British navy started. Also in 1680, Maratha kingdom underwent great disaster of Shivaji's death. Taking advantage of this unstable situation, Siddi captured the Underi island & without wasting any time constructed fort on it.
In 1681, Balaji Pilaji Tabib promised Sambhaji that he will take Underi. He attacked Underi alongwith Maaynak Bhandari but failed.
Underi was very important as it was placed between Thal & Khanderi. Hence even Peshwe tried to conquer it in 1732 & 1733 but yet again returned with failure. In 1736, Chimaji Appa & manaji Angre opned front against Siddi Saat who was then Chief of the fort. Siddi Saat was killed but fort couldnot be taken.
In 1758, Tukaji Angre Sieged the fort but could not conquer. In 1759, Nanasaheb Peshwe himself with Sarkhel Angrelead the mission. This time troops reached till walls of Underi, but once again failed to conquer.
Finally after 80 years, in 1760 Naro Trimbak, officer of Peshwe took the fort successfully. Peshwe rightly named it "Jaidurg".
In 1774, Siddi attempted to conquer Underi but failed.
How to Reach
One can travel to Thaal by ST bus. From Thaal, one has to negotiate with local fishermen to take you to the fort.