TANHAJI: THE UNSUNG WARRIOR is the story of one of the greatest warriors of India. The year is 1664. Chhatrapati Shivaji Maharaj (Sharad Kelkar) has given a tough fight to the Mughals, headed by Emperor Aurangzeb (Luke Kenny), in the Deccan region.
However, when things get tough for the Marathas, Shivaji Maharaj decides to sign a treaty. As part of this agreement, he hands over some 23 forts to the Mughals, including the strategic Kondhana Fort. A few years later, Chhatrapati Shivaji Maharaj expresses his desire to recapture Kondhana. This is especially when he finds out that Aurangzeb has sent Udaybhan Rathod (Saif Ali Khan), an evil military officer, to control the fort. Chhatrapati Shivaji Maharaj realizes that his brave Subedar Tanaji Malusare (Ajay Devgn) is the best man to get the fort back. But Chhatrapati Shivaji Maharaj refuses to even let Tanaji know about this operation. This is because Tanaji is busy with the marriage of his son.
However, Tanaji finds out about the plan. He persuades Chhatrapati Shivaji Maharaj to let him go for it. The Maharaj agrees and hence, Tanaji keeps his son's marriage on hold. He then begins to plan how to recapture the fort and thereby create history. What happens next forms the rest of the film.