Israel, Divided into 2 kingdoms

Initially all Israel was united under the judges, and then under King Saul.

The first mention of the 12-tribe nation of Israel being divided into two kingdoms, Southern Kingdom vs Northern Kingdom, Judah vs Israel, Jacob vs Joseph (Joseph alluding to his son Ephraim, the most prominent tribe of the Northern Kingdom), is when David was crowned King of Judah at Hebon (2 Samuel 2.4) while the ten tribes of the north remained loyal to the House of deceased King Saul, with Saul's son Ish-Bosheth ruling in Mahanaim (2 Sam 2.8-10).

David began his reign at Hebron at 30 years of age (2 Sam 5.4).

The warfare between the two kingdoms raged for 7 1/2 years (2 Sam 5.5), and is documented in 2 Sam 2.12-4.12. It ended with the defection of Ish-Bosheth's general Abner to King David (2 Sam 3.6-21), followed by the assassination of Ish-Bosheth (2 Sam 4.1-12).

All Israel was then united once again under one King (David, 2 Sam 5.1-3). David had reigned over Judah 7 1/2 years from Hebron, and then he reigned over all Israel, mostly from Jerusalem, for 33 years (2 Sam 5.4-5, 1 Ki 2.11).

All Israel remained under one king for the 33-year reign of David and the 40-year reign of his son Solomon. During this time there persisted an awareness of the "north-south" division of the nation, as evidenced by David's terminology when he said he had made Solomon ruler, "over Israel and Judah" (1 Ki 1.35).

Due to Solomon's unfaithfulness to God (1 Ki 11.1-10), God told Solomon He would, after Solomon's death, tear the kingdom away from him, e.g. from his son (Rehoboam, 1 Ki 11.43), and give it to one of his (Solomon's) subordinates (1 Ki 11.11-13); and would leave Solomon's son with only one tribe (1 Ki 11.13, 32, 36) over which to rule from Jerusalem (1 Ki 11.36). God employed Ahijah, His prophet at Shiloh, to inform Jeroboam, Solomon's manager of city construction (1 Ki 11.26-28), that he would be the ruler God planned for the soon-to-be northern kingdom, which God called "Israel" (1 Ki 11.37). Ahijah told Jeroboam that God would give him rule over those 10 tribes (1 Ki 11.29-39).

The split, caused by Rehoboam's unwise promise to be a harsh ruler (1 Ki 12.1-14), his lack of wisdom caused by God (1 Ki 12.15), occurred just days afte Rehoboam's coronation (1 Ki 12.1, 16, 18-19), the tribe of Judah remained loyal to Rehoboam (1 Ki 12.17), as apparently did also the tribe of Benjamin (1 Ki 12.21, 23). Per God's plan, the rebelling 10 tribes made Jeroboam king over them (1 Ki 12.20).

Jeroboam, fearing a resurgence of Israelites' loyalty to the house of David if they regularly returned to Jerusalem for the mandated feasts, violated God's law (Dt 12.4-14) and established two places of worship, one in Bethel and one in Dan, each equipped with a golden calf-idol (1 Ki 12.26-30). He further violated God by building shrines on high places, appointing priests not of the tribe of Levi, and instituting feasts in addition to and contrary to those mandated by God (1 Ki 12.31-33).