Deuteronomy 2:26 (ESV)

26 “So I sent messengers from the wilderness of Kedemoth to Sihon the king of Heshbon, with words of peace, saying,

The campaign against Sihon began on a peaceful note, with messengers sent ahead of the group to speak words of peace to the Amorite king, whose capital city was Heshbon. The main body of Israel remained in the wilderness of Kedemoth, likely a few miles inside Sihon's territory.