▁ac quire ▁the ▁imported ▁goods ▁it ▁required ▁through ▁inter medi ary ▁trade ▁with ▁the ▁Dutch ▁and ▁through ▁the ▁Ry uky u ▁Islands . ▁The ▁Japanese ▁actually ▁encourag ed ▁the ▁Ry ū ky ū ▁Kingdom ' s ▁r ul ers ▁to ▁maintain ▁a ▁trib ut ary ▁relationship ▁with ▁China , ▁even ▁though ▁the ▁Sh im azu ▁cl an ▁had ▁sur re pt it iously ▁established ▁great ▁political ▁influence ▁in ▁the ▁Ry uky u ▁Islands . ▁The ▁Q ing ▁became ▁much ▁more ▁open ▁to ▁trade ▁after ▁it ▁had ▁defeated ▁the ▁M ing ▁loyal ists ▁in ▁Taiwan , ▁and ▁thus ▁Japan ' s ▁r ul ers ▁felt ▁even ▁less ▁need ▁to ▁establish ▁official ▁relations ▁with ▁China . ▁ ▁Liberal izing ▁challeng es ▁to ▁s ak oku ▁did ▁come ▁from ▁within ▁Japan ' s ▁el ite ▁in ▁the ▁ 1 8 th ▁century , ▁but ▁they ▁came ▁to ▁nothing . ▁Later ▁on , ▁the ▁s ak oku ▁policy ▁was ▁the ▁main ▁saf egu ard ▁against ▁the ▁total ▁de ple tion ▁of ▁Japanese ▁min eral ▁resources — such ▁as ▁silver ▁and ▁co pper — to ▁the ▁outside ▁world . ▁However , ▁while ▁silver ▁export ation ▁through ▁Nag as aki ▁was ▁controlled ▁by ▁the ▁sh og un ate ▁to ▁the ▁point ▁of ▁stopping ▁all ▁export ation , ▁the ▁export ation ▁of ▁silver ▁through ▁Korea ▁continued ▁in ▁relatively ▁high ▁quantities . ▁ ▁The ▁way ▁Japan ▁kept ▁ab re ast ▁of ▁Western ▁technology ▁during ▁this ▁period ▁was ▁by ▁studying ▁medical ▁and ▁other ▁texts ▁in ▁the ▁Dutch ▁language ▁obtained ▁through ▁De j