Conquering Jerusalem presented a formidable challenge for the Israelites as they entered the land, leaving the city as a foreign enclave for an extended period. Although the effort to drive out the local inhabitants was spearheaded by the tribe of Judah, Jerusalem was actually a shared city. A strip of land extended from Judah's borders directly into the territory of the tribe of Benjamin, making the city a joint inheritance [מצודת דוד, אברבנאל, ביאור שטיינזלץ].
The identity of the people defending this stronghold is viewed in two distinct ways. The primary approach understands them simply as the local nation residing in the area [מצודת דוד, אברבנאל]. A midrashic perspective, however, suggests a different origin, asserting that "Yevus" was not a nation at all. Instead, it was either a specific Philistine man descended from Abimelech who built the city, or the name of a distinct district in Jerusalem where the Tower of David stood, which was populated by Philistines [רש״י, רד״ק, אברבנאל].
The inability of the tribe of Judah to drive out these inhabitants carried a dual historical significance. A subtle shift in the traditional recording of these events—blending the past and future tenses—reveals that the tribe of Judah not only failed to capture the stronghold during the initial conquest, but they were destined to remain unable to do so long into the future, right up until the era of King David [מנחת שי, רד״ק].
The commentators offer two reasons for this long-standing inability to capture the city. On a practical level, the fortress in Jerusalem was exceptionally strong, and the tribe of Judah simply lacked the military power to breach its walls [רד״ק, אברבנאל]. Furthermore, this military stalemate may have been the result of direct guidance from God. God ensured the fortress would remain untaken so that it could be preserved specifically for David, eventually becoming the capital of the Israelite kingdom and bearing his name [רד״ק].
A contrasting midrashic approach argues that the limitation was not military, but moral. The tribe of Judah possessed the physical might to conquer the city, but they were legally forbidden from doing so. Generations earlier, Abraham had sworn an oath of peace to the Philistine king Abimelech, an agreement binding for three generations. Because the inhabitants of Yevus were tied to Abimelech's lineage, and his grandson was still alive during the initial conquest of the land, the Israelites were barred from attacking. It was only during the reign of King David, after the grandson had passed away and the oath expired, that the Israelites were finally permitted to conquer the fortress and rightfully acquire the area [רש״י, רד״ק, אברבנאל].
As a result, the original inhabitants continued to live side-by-side with the tribe of Judah. This shared, unresolved reality persisted through the era when the Book of Joshua was recorded and into the period of the Judges, ending only with the final and complete conquest of Jerusalem by King David [רד״ק, ביאור שטיינזלץ, אברבנאל].