The Yan-Isleth, also known as the Brotherhood of the Sword, were an elite military unit of Klingon warriors that served as the personal security force for the Chancellor of the High Council of the Klingon Empire. (DS9 episode: "Apocalypse Rising")
The Yan-Isleth remained loyal to Chancellor Gowron after Worf killed him on Deep Space 9 at the end of the Dominion War. Chancellor Martok tried to disband them, while Emperor Kahless undermined them. Neither were successful, and the Yan-Isleth remained in control of Ty'Gokor into 2376. (DS9 - The Left Hand of Destiny novel: Book Two)
- As many chancellors (such as L'Rell, Gowron and Martok) have been seen to take command of Klingon Defense Force vessels and lead attacks personally - while still remaining in the office of Chancellor - it's likely that those vessels contained a detachment of Yan-Isleth aboard.