But YHVH said to me, ‘Do not fear him, for I have given him and all his people and his land into your hand. And you shall do to him as you did to Sihon the king of the Amorites, who lived at Heshbon.’
Deuteronomy 3:2

King Og was a survivor. Legend says that he survived the Flood and many wars, even that he knew Abraham personally. Everyone feared him, but God told Moses, "Don't fear King Og. I have already given him into your hand. He just doesn't know it yet." Once set in motion, God's promises are as sure as a tidal wave. Faith in his name (trust in his character & acting on that trust) enables us to partake in those promises.