=Establishment of Jerusalem as Israel's Capital.= David's first act as king of all Israel was to break down the barrier of Canaanite cities which separated the north from the south, and then to establish a capital that would be free from local associations and more central than his former capital at Hebron. The Jebusite city of Jerusalem fully satisfied these conditions and was at the same time by nature much stronger and better fortified than Hebron. The original city of David apparently included the old Jebusite city on the hill of Ophel^{(55)} with certain additions, known as Millo, probably running down into one of the adjacent valleys.^{(95)} Possibly, during the reigns of David and Solomon, the dwelling-places of the Hebrews began to climb across the Tyropœon Valley (_cf._ p. 65) and up the western hill, but there is no evidence that at this early date the western town was surrounded by a wall and thus incorporated in the City of David. =Israel's Natural Boundaries.= With the establishment of the new capital at Jerusalem and the transference thither of the ark from Kirjath-jearim, the various Hebrew tribes were brought into a close political and religious union. The prestige and tactful, conciliatory policy of David were important factors in bringing about this union. The process was also hastened by the pressure of outside foes and by the aggressive policy toward them which David at once initiated. On the west and north the territory of Israel had reached its natural bounds. Never again did the Philistines make a determined endeavor to override the barrier of the western hills and conquer the land of the Hebrews. The Phœnicians were, by virtue of their position, a commercial people with no ambitions for military conquest. On the east and south, however, Israel's natural bounds were the desert. As long as there were strong nations like the Ammonites and Moabites on the east, separated from the Hebrews only by artificial bounds, there was no guarantee of permanent peace. The past history of Palestine had fully demonstrated this truth and David was not slow in acting in accordance with it.