However, because in the latter half of the seventh century the Japanese army was defeated by the Allied Forces of Tang Dynasty and Silla Kingdom in Hakusukinoe (Baekgang jeontu) in the Korean peninsula, the castle may have been built as a militant stronghold against their attacks.
しかし、7世紀後半、倭軍が朝鮮半島の白村江で唐・新羅の連合軍に敗れて、その来寇に備える軍事拠点と位置づけられて築城されたものであろう。