David (reigned 1007 - 970 BC) succeeded Saul's Jonathan, and was portrayed as an ideal king as opposed to the flawed Saul. David's capture of Jerusalem established the United Monarchy.
However, David ruled from Hebron because Jerusalem was not the seat of Israelite power yet. David, like his successor Solomon, was essentially a warlord ruling a territorial kingdom, which requires a minimal of formal bureaucracy (forts/palaces/etc).
David conquered Jerusalem in 1,000 BC (2 Sam. 5:6-10).
David consecrated it as the political and religious capital by building a palace there using timber and craftsmen supplied by Hiram of Tyre (2 Sam. 5:11-12) and by giving the ark of the covenant permanent residence in Jerusalem in its tabernacle.
David was a vigorous military campaigner.
David then successfully warred against the Philistines, whose movement to the east placed them in direct conflict with the Israelites (Exodus 12:41), and repulsed them out of Canaan. Next, David embarked on a series of clockwork military campaigns to defeat: Moabites (2 Sam. 8:2); Aramaeans of Zobah, led by Hadadezer (2 Sam. 8:3f); Aramaeans of Damascus (2 Sam 8:5-8); Hamath, indicated by a tribute by David (2 Sam 8:9f); Edomites (2 Sam 9:13f); Ammonites (2 Sam. 10:1-14; 11:1); and the Amalekites (2 Sam. 8:12).
His son Abasalom attempted a coup (2 Sam. 16:15–18:18), after which David embarked on more wars against Philistines (2 Sam. 21:15–22).