Now Joab was over all the host of Israel: and Benaiah the son of Jehoiada was over the Cherethites and over the Pelethites: Joab was over all the host - He had murdered Amasa, and seized on the supreme command: and such was his power at present, and the service which he had rendered to the state by quelling the rebellion of Sheba, that David was obliged to continue him; and dared not to call him to account for his murders without endangering the safety of the state by a civil war.
Benaiah - over the Cherethites - Benaiah was over the archers and slingers.
See the notes on 2 Samuel 8:18.