In addition to leading David’s army to victory on multiple occasions, Joab may have been David’s hitman. Let’s look at three instances described in 2nd Samuel that illuminate Joab’s nature.
First, in 2nd Samuel 3, after Saul’s death, David’s rise to power in Judah, and fighting between David and Saul’s son Ish-Bosheth of Israel, Abner, the military leader of Israel to the north and Joab’s counterpart, defects to David. According to the text, upon learning of Abner’s defection, Joab intercepts the traveling Abner and kills him. The text is clear in pointing out that David had no forehand knowledge of Joab’s intent to kill Abner.
Second, in 2nd Samuel 18, Absalom, after he has murdered David’s eldest son, has usurped David’s throne, and has made war with David gets his head stuck in a tree as he is riding on his mule. When news of this incident reaches Joab on the battlefield, Joab, after insulting the messenger, quickly impales Absalom with three javelins. We are reminded by the messenger, as he describes the situation to Joab, that David had given instructions not to harm Absalom.
Third, in 2nd Samuel 20, David instructed Amasa, who had been made captain of the army by Absalom and was Joab’s cousin, to pursue Sheba, the leader of the current rebellion. Amasa delayed in carrying out his orders. Upon meeting up with Joab later during the pursuit of Sheba, Joab, with one deceitful left-handed jab to the gut, kills Amasa. No mention is made of David’s response to Amasa’s delay.
In all three scenarios, Joab had a motive to murder. The defecting Abner was a potential threat to Joab’s military position. Absalom would likely have had Joab executed once David was defeated. Amasa was another threat to Joab’s position.
Additionally, David also had a motive for murder. Abner had been the military leader of David’s enemy, and his defection may have been a trick. Absalom had killed his eldest son, taken his kingdom, and was currently seeking his life. Amasa had delayed obeying David’s order allowing the rebel Sheba to potentially escape.
Though the text either explicitly or through silence denies David’s involvement in these deaths, Joab as hitman fits the story better than Joab as an unruly murderer that David continues to keep as his “right-hand” man.
One further clue to Joab as David’s hitman is the whole business with Uriah. David sends Uriah to Joab with a note telling Joab to put Uriah at the front of the battle and then to draw the rest of the men back leaving Uriah to die. Joab did this. No motive is presented for Joab to have caused Uriah’s death. At the very least, in this instance, Joab acted as David’s hitman, and this presents a lens through which we may view the previous three murders.
For more on Joab as a political maneuverer, see this page.
If you are considering Joab as a baby name, see this page.