1 Chronicles 10-12
King Saul was the first human king of Israel (see Israelite Monarchy - The Origin). Unfortunately, for Saul, and for Israel, Saul proved himself to be an unstable and unwise leader. While fighting David (see Israelite Monarchy - The Civil War), Saul also fought Israel's actual enemies, the Philistines - a conflict that cost Saul his life.
"Now the Philistines fought against Israel; and the men of Israel fled before the Philistines, and fell slain on Mount Gilboa. And the Philistines overtook Saul and his sons; and the Philistines slew Jonathan and Abinadab and Malchishua, the sons of Saul. The battle pressed hard upon Saul, and the archers found him; and he was wounded by the Archers.
Saul's dead body was abused; his head was taken as a Trophy, while the body was later recovered by Israel.
"On the morrow, when the Philistines came to strip the slain, they found Saul and his sons fallen on Mount Gilboa. And they stripped him and took his head and his armor, and sent messengers throughout the land of the Philistines, to carry the good news to their idols and to the people. And they put his armor in the temple of their gods, and fastened his head in the temple of Dagon [see also The Pillars Of Dagon's Temple].
Although Saul was an unwise leader, it was his unfaithfulness to The Lord that caused The Lord to replace Saul with David.
"So Saul died for his unfaithfulness; he was unfaithful to The Lord in that he did not keep the command of The Lord, and also consulted a medium, seeking guidance, and did not seek guidance from The Lord. Therefore The Lord slew him, and turned the kingdom over to David the son of Jesse." (1 Chronicles 10:13-14 RSV)
1 Chronicles Chapter 11
The death of Saul ended the civil war (that one, anyway) and produced The United Kingdom of Israel under David.
"Then all Israel gathered together to David at Hebron [see David's Capital During The Civil War], and said, "Behold, we are your bone and flesh. In times past, even when Saul was king, it was you that led out and brought in Israel; and The Lord your God said to you, 'You shall be shepherd of my people Israel, and you shall be prince over my people Israel.'"
David then transferred his capital to Jerusalem, which he captured from the Jebusites.
"And David and all Israel went to Jerusalem, that is Jebus, where the Jebusites were, the inhabitants of the land. The inhabitants of Jebus said to David, "You will not come in here." Nevertheless David took the stronghold of Zion, that is, the city of David.
1 Chronicles Chapter 12
David's rise to the throne was neither easy or swift, but it was an inevitable result of the people recognizing the right man to lead them (see Royal Democracy).
"Now these are the men who came to David at Ziklag, while he could not move about freely because of Saul the son of Kish; and they were among the mighty men who helped him in war. They were bowmen, and could shoot arrows and sling stones with either the right or the left hand; they were Benjaminites, Saul's kinsmen." (1 Chronicles 12:1-2 RSV)
The end result was that The Lord's choice for king became king. It was cause for celebration.
"All these, men of war, arrayed in battle order, came to Hebron with full intent to make David king over all Israel; likewise all the rest of Israel were of a single mind to make David king. And they were there with David for three days, eating and drinking, for their brethren had made preparation for them. And also their neighbors, from as far as Issachar and Zebulun and Naphtali, came bringing food on asses and on camels and on mules and on oxen, abundant provisions of meal, cakes of figs, clusters of raisins, and wine and oil, oxen and sheep, for there was joy in Israel." (1 Chronicles 12:38-40 RSV)