Sihon was the Amorite king of Heshbon whom Israel defeated east of the Jordan after he refused Moses' request for peaceful passage.
Biography
Numbers 21 and Deuteronomy recount Moses asking Sihon for passage through his territory with promises not to turn aside into fields or vineyards. Sihon instead gathered his army and attacked Israel at Jahaz. Israel defeated him and occupied his territory from the Arnon toward the Jabbok. The victory over Sihon, together with Og, was repeatedly remembered as evidence of God's power.
Biblical Significance
Sihon's defeat opened substantial territory east of the Jordan to Israel and became a recurring biblical example of God's deliverance before the conquest of Canaan.