When Sihon and all his troops emerged to encounter us in battle at Jahaz,

This took place after the defeat of King Sihon of the Amorites, whose capital was in Heshbon, and King Og of Bashan, whose capital was in Ashtaroth, specifically in Edrei.

The Lord said to me, “Look! I have already begun to give over Sihon and his land to you. Start right now to take his land as your possession.”

When you came to this place King Sihon of Heshbon and King Og of Bashan came out to make war and we defeated them.

Get up, make your way across Wadi Arnon. Look! I have already delivered over to you Sihon the Amorite, king of Heshbon, and his land. Go ahead! Take it! Engage him in war!

But King Sihon of Heshbon was unwilling to allow us to pass near him because the Lord our God had made him obstinate and stubborn so that he might deliver him over to you this very day.

in the Transjordan, in the valley opposite Beth Peor, in the land of King Sihon of the Amorites, who lived in Heshbon. (It is he whom Moses and the Israelites attacked after they came out of Egypt.