Deuteronomy 2:26

And I sent messengers out of the wilderness of Kedemoth unto Sihon king of Heshbon with words of peace, saying,

Deuteronomy 2:26 belongs to Israel's northward march toward the Jordan and the promised land after passing Edom and Moab. Israel passed to the east of Moab because God had forbidden taking Moabite land given to the descendants of Lot, with the same direction applying to the Ammonites as descendants of Lot. The Amorites were a strong and warlike people who had moved from the southern part of Canaan across the Jordan, made war on the Moabites, taken part of their territory, and ruled undisputed from the Arnon as far north as the Jabbok, so Israel's desired route to the Jordan lay directly through their territory. Moses therefore sent a friendly message to Sihon the Amorite king at his capital asking only to pass through on foot by the highway without turning to the right or left, offering to buy meat and water with money.

Sihon answered with decided refusal and summoned all the hosts of the Amorites to oppose Israel, leaving poorly prepared Israel facing well-armed and well-disciplined forces that to all human appearance would quickly destroy them. The message led to Israel crossing the river Arnon, advancing upon Sihon, defeating his armies in battle, and taking possession of the country of the Amorites. The victory was won by the Captain of the Lord's host vanquishing His people's enemies, the same victory He would have given thirty-eight years before if Israel had trusted Him.