Now that Saul was dead, David may have been tempted to make himself king in his stead, but continuing his course of dependence on God, he inquired of Him, "Shall I go up into any of the cities of Judah?" and "Whither shall I go up?" Judah was David's own tribe; and Hebron, where he was directed to go, was the region in which Abraham and Sarah, Isaac and Jacob had lived and were buried, about 20 miles south of Jerusalem. Having arrived there with his two wives and his men and their families. David was anointed king of the tribe by the men of Judah. He was now thirty years of age (chapter 5:4).
Upon David's being told of the burial of Saul's body by the courageous men of Jabesh-gilead, he sent messengers to thank them and to tell them that he had been made king over the tribe of Judah. Five years appear to have passed without the other tribes of Israel having taken any steps to fill the dead king Saul's place. Then, though God had long before (1 Samuel 16) made known through Samuel the prophet, His purpose that 'David should be the next king, Ish-bosheth, the only remaining son of Saul, was made king over the people of Israel. It was Abner, the leader of Saul's army and Saul's cousin, who brought about the crowning of Ish-bosheth at Mahanaim, a place east of the Jordan quite close to Jabesh-gilead in the land of Gad.
It appears to have been Abner's purpose to get rid of David when he led an expedition as far as Gibeon, a few miles northwest of Jerusalem. There they were met by Joab, David's nephew, who became the head of his army, but a bold unscrupulous, self-seeking man who afterward murdered Abner and Amasa and was himself put to death (1 Kings 2:31-3431And the king said unto him, Do as he hath said, and fall upon him, and bury him; that thou mayest take away the innocent blood, which Joab shed, from me, and from the house of my father. 32And the Lord shall return his blood upon his own head, who fell upon two men more righteous and better than he, and slew them with the sword, my father David not knowing thereof, to wit, Abner the son of Ner, captain of the host of Israel, and Amasa the son of Jether, captain of the host of Judah. 33Their blood shall therefore return upon the head of Joab, and upon the head of his seed for ever: but upon David, and upon his seed, and upon his house, and upon his throne, shall there be peace for ever from the Lord. 34So Benaiah the son of Jehoiada went up, and fell upon him, and slew him: and he was buried in his own house in the wilderness. (1 Kings 2:31‑34)).
We cannot think that David was led of God to send out Joab and others to meet the followers of Saul's son, or that the fighting that took place was according to His mind, where Israelite killed Israelite. It is a sad part of David's history.