Introduction:
Joab, the son of Zeruiah, was a prominent military commander in the service of King David. Known for his strategic acumen and fierce loyalty to David, Joab played a crucial role in the establishment and consolidation of David's kingdom. His interventions, often marked by a blend of political savvy and ruthless action, are recorded in the books of Samuel and Kings. Joab's actions, while sometimes controversial, were pivotal in shaping the course of Israel's history during David's reign.

Intervention in Abner's Defection:
One of Joab's significant interventions occurred during the power struggle between the house of Saul and David. Abner, the commander of Saul's army, defected to David, seeking to bring the tribes of Israel under David's rule (2 Samuel 3:12-21). Joab, suspicious of Abner's motives and seeking to avenge his brother Asahel's death at Abner's hands, took matters into his own hands. Despite David's peace treaty with Abner, Joab deceitfully lured Abner back to Hebron and killed him (2 Samuel 3:26-27). Joab's actions, while avenging his brother, complicated David's efforts to unify the kingdom and forced David to publicly distance himself from the murder (2 Samuel 3:28-39).

Intervention in the Siege of Rabbah:
Joab also played a critical role in the siege of Rabbah, the Ammonite capital. After leading the initial assault and capturing the city's water supply, Joab sent word to David to come and claim the final victory, ensuring that the glory of the conquest would belong to the king (2 Samuel 12:26-29). This intervention demonstrated Joab's loyalty to David and his understanding of the importance of royal prestige in maintaining the king's authority.

Intervention in Absalom's Rebellion:
During Absalom's rebellion, Joab's intervention was decisive. Despite David's explicit command to deal gently with Absalom, Joab recognized the threat Absalom posed to the kingdom's stability. When Absalom was found hanging by his hair in a tree, Joab took the initiative to kill him, thereby quelling the rebellion (2 Samuel 18:9-15). Joab's actions, though contrary to David's wishes, were driven by a pragmatic understanding of the need to eliminate threats to the throne.

Intervention in David's Census:
Joab also intervened during David's ill-fated decision to conduct a census of Israel and Judah. Despite his reservations and attempts to dissuade the king, Joab carried out the order, albeit reluctantly (2 Samuel 24:1-9). The census, which was seen as an act of pride and lack of trust in God's provision, led to divine judgment upon Israel. Joab's intervention here highlights his complex relationship with David, balancing obedience with his own understanding of God's will.

Intervention in Adonijah's Ambition:
As David's reign drew to a close, Joab supported Adonijah's bid for the throne, contrary to David's wishes for Solomon to succeed him (1 Kings 1:5-7). This intervention ultimately led to Joab's downfall. After Solomon's ascension, Joab sought refuge at the altar but was executed on Solomon's orders, marking the end of his influential yet tumultuous career (1 Kings 2:28-34).

Conclusion:
Joab's interventions throughout his life were marked by a complex interplay of loyalty, ambition, and pragmatism. His actions, while often controversial, were instrumental in shaping the political landscape of Israel during one of its most formative periods.