David and all Israel marched to Jerusalem (that is, Jebus); the Jebusites who inhabited the land were there.
References for 1 Chronicles 11:4
The inhabitants of Jebus said to David, "You will never get in here." Yet David did capture the stronghold of Zion (that is, the city of David).
David said, "Whoever is the first to kill a Jebusite will become commander-in-chief." Joab son of Zeruiah went up first, so he became the chief.
Then David took up residence in the stronghold; therefore, it was called the city of David.
He built up the city all the way around, from the supporting terraces to the surrounding parts, and Joab restored the rest of the city.
David steadily grew more powerful, and the Lord of Hosts was with him.
References for 1 Chronicles 11:9