Chimmaji Appa (or Chimaji Appa) (Marathi: चिमाजी अप्पा) (1707–1741) was the son of Balaji Vishwanath Bhat and the younger brother of Bajirao Peshwa of Maratha Empire. He was an able military commander who liberated the western coast of India fromPortuguese rule. The crowning glory of his career was the capture of Vasai fort from the Portuguese (who had technically advanced weapons and artillery at their disposal) in a hard fought battle. Do not get confused between Chimaji Appa and Chimnaji Appa as Chimaji Appa was the son of Balaji Vishwanath Bhat and younger brother of Bajirao-1and Chimnaji Appa was the posthumous son born to Anandibai, the wife of Raghunathrao.
Source : Wikipedia