In Japan, sakimori was deployed for the defense of outlying territories such as the coast of Kyushu due to the fear of a possible invasion by Tang Dynasty China after the major defeat suffered by Japanese troops, who had been dispatched to aid Baekje on the Korean peninsula, by the allied forces of Tang Dynasty China and the Silla Kingdom at the Battle of Baekgang in 663.
日本の防人は、大化の改新の後、663年に朝鮮半島の百済救済のために出兵した倭軍が白村江の戦いにて唐・新羅の連合軍に大敗したことを契機に、唐が攻めてくるのではないかとの憂慮から九州沿岸の防衛のため設置された辺境防備の兵である。