Deuteronomy 3:5

All these cities were fenced with high walls, gates, and bars; beside unwalled towns a great many.

Og's territory of Bashan was a powerful, populous kingdom holding many cities fenced with high walls, gates, and bars. Beside those walled cities lay a great many unwalled towns, showing how populous the kingdom was. Israel therefore faced as they entered the land both imposing fortified cities and numerous smaller settlements. Its great stone buildings and strongholds made the land appear impregnable. That appearance tested Israel's courage and faith in God.

Even so powerful a king as Og could not withstand Israel, nor could his fortified cities hold out against them. The defeat of Og and his territory demonstrated that human strength and walled defenses were no barrier when God fought for Israel. The victory over Bashan helped fill the neighboring nations with fear of Israel.