▁the ▁ 3 8 th ▁Infantry ▁Division ), ▁and ▁the ▁division ▁reserve ▁led ▁by ▁Mar uy ama ▁compr ising ▁the ▁ 1 6 th ▁Infantry ▁Regiment . ▁The ▁date ▁of ▁the ▁attack ▁was ▁set ▁for ▁ 2 2 ▁October . ▁To ▁dist ract ▁the ▁Americans ▁from ▁the ▁planned ▁attack ▁from ▁the ▁south , ▁Hy ak ut ake ' s ▁heavy ▁art illery ▁plus ▁five ▁batt al ions ▁of ▁inf antry ▁( about ▁ 2 , 9 0 0 ▁men ) ▁under ▁Major ▁General ▁T ad ashi ▁Sum iy oshi ▁were ▁to ▁attack ▁the ▁American ▁def enses ▁from ▁the ▁west ▁along ▁the ▁coast al ▁cor rid or . ▁The ▁Japanese ▁estimated ▁that ▁there ▁were ▁ 1 0 , 0 0 0 ▁American ▁troops ▁on ▁the ▁island , ▁when ▁in ▁fact ▁there ▁were ▁about ▁ 2 3 , 0 0 0 . ▁ ▁At ▁this ▁time , ▁the ▁L ung a ▁per imeter ▁was ▁def ended ▁by ▁four ▁American ▁reg iments ▁compr ising ▁ 1 3 ▁inf antry ▁batt al ions . ▁The ▁ 1 6 4 th ▁Infantry ▁Regiment ▁guard ed ▁the ▁eastern most ▁sector . ▁Ext ending ▁from ▁the ▁ 1 6 4 th ▁south ▁and ▁west ▁across ▁Ed son ' s ▁R idge ▁to ▁the ▁L ung a ▁River ▁was ▁the ▁ 7 th ▁Marine ▁Regiment ▁under ▁Colonel ▁Am or ▁L . ▁Sim s . ▁Cover ing ▁the ▁sector ▁west ▁of ▁the ▁L ung a ▁to ▁the ▁coast ▁were ▁the ▁ 1 st ▁and ▁ 5 th ▁Marine ▁Reg iments . ▁Def