Introduction:
Joab, the son of Zeruiah, was a prominent military commander in the service of King David. Known for his strategic prowess and loyalty to David, Joab's career was also marked by acts of treachery that had significant implications for the kingdom of Israel. His actions, often driven by personal ambition and a ruthless approach to power, provide a complex portrait of a man who was both a loyal servant and a dangerous adversary.

Murder of Abner:
One of Joab's most notorious acts of treachery was the murder of Abner, the son of Ner. Abner had been the commander of Saul's army and later sought to transfer the allegiance of Israel to David. Despite David's peaceful intentions, Joab, motivated by revenge for the death of his brother Asahel at Abner's hands, deceitfully lured Abner back to Hebron and killed him. This act is recorded in 2 Samuel 3:27: "Now when Abner returned to Hebron, Joab took him aside into the gateway to speak with him privately, and there he stabbed him in the stomach. So Abner died in revenge for the blood of Asahel, Joab’s brother."

Murder of Amasa:
Joab's treachery continued with the murder of Amasa, whom David had appointed as commander of the army in place of Joab. In 2 Samuel 20:9-10, Joab deceitfully greeted Amasa with a kiss and then killed him: "Joab said to Amasa, 'Are you well, my brother?' And with his right hand Joab took hold of Amasa’s beard to kiss him. But Amasa was not on guard against the dagger in Joab’s hand, and Joab stabbed him in the stomach and spilled his intestines on the ground. He did not need to strike him again, and Amasa died."

Role in Absalom's Rebellion:
Joab's relationship with David was further complicated during Absalom's rebellion. Although Joab initially supported David, he later acted against the king's explicit orders by killing Absalom. In 2 Samuel 18:14-15, Joab took three javelins and thrust them into Absalom's heart while he was still alive in the oak tree, and his armor-bearers finished him off. This act, while ending the rebellion, was a direct defiance of David's command to deal gently with Absalom.

Support for Adonijah:
In the latter years of David's reign, Joab aligned himself with Adonijah, David's son, who attempted to usurp the throne. This political maneuvering is detailed in 1 Kings 1:7: "So Adonijah conferred with Joab son of Zeruiah and with Abiathar the priest, who supported him." Joab's support for Adonijah was a significant betrayal of David's wishes for Solomon to succeed him.

Death of Joab:
Joab's life ended in retribution for his many acts of treachery. After Solomon ascended to the throne, he ordered Joab's execution for his past murders and his support of Adonijah. Joab fled to the tent of the LORD and took hold of the horns of the altar, but Solomon's commander Benaiah was sent to carry out the execution. 1 Kings 2:31-34 records this event: "The king replied to him, 'Do as he says. Strike him down and bury him, and so clear me and my father’s house of the guilt of the blood that Joab shed without cause.'"

Conclusion:
Joab's life and actions serve as a cautionary tale of the dangers of unchecked ambition and the consequences of betrayal. His account is interwoven with the history of David's reign, illustrating the complexities of loyalty, power, and justice in the biblical narrative.