The imperial court then realized that they must open up the more remote regions to settlement in order to better protect it from external aggression.
至於依舊是「化外之地」的東部，只能靠偶爾的巡防帆船防守。因此當時的邊防，可謂「前山拒虎」，後山則時有「狼進之患」。要想防衛後山，定得鼓勵百姓到後山開墾。