Emperor Tenchi prepared for reprisal and invasion from the Tang and Silla forces, and built mizuki castles (castles on lakes or marshes for defensive reasons) in the local government capital in Northern Kyushu, installed defensive structures in the old mountain castles in each area of West Japan, and posted soldiers on the sea line of Northern Kyushu.
天智天皇は唐・新羅による報復と侵攻に備え、北部九州の大宰府の水城（みずき）や西日本各地の古代山城などの防衛施設を築き、北部九州沿岸には防人（さきもり）を配備した。