▁sh oring ▁up ▁and ▁strength ening ▁their ▁L ung a ▁def enses . ▁On ▁ 1 8 ▁September , ▁an ▁Al lied ▁naval ▁con voy ▁delivered ▁ 4 , 1 5 7 ▁men ▁from ▁the ▁U . S . ▁ 7 th ▁Marine ▁Regiment ▁to ▁Gu adal can al . ▁This ▁regiment ▁had ▁previously ▁formed ▁part ▁of ▁the ▁ 3 rd ▁Pro vis ional ▁Marine ▁Brigade ▁and ▁was ▁fresh ▁from ▁g arrison ▁duty ▁in ▁Sam oa . ▁These ▁rein for c ements ▁allowed ▁V ande gr ift , ▁beginning ▁on ▁ 1 9 ▁September , ▁to ▁establish ▁an ▁un bro ken ▁line ▁of ▁defense ▁completely ▁around ▁the ▁L ung a ▁per imeter . ▁ ▁General ▁V ande gr ift ▁and ▁his ▁staff ▁were ▁aware ▁that ▁K aw ag uch i ' s ▁troops ▁had ▁retre ated ▁to ▁the ▁area ▁west ▁of ▁the ▁Mat an ik au ▁and ▁that ▁numerous ▁groups ▁of ▁Japanese ▁st rag gl ers ▁were ▁scattered ▁throughout ▁the ▁area ▁between ▁the ▁L ung a ▁per imeter ▁and ▁the ▁Mat an ik au ▁River . ▁V ande gr ift , ▁therefore , ▁decided ▁to ▁conduct ▁a ▁series ▁of ▁small ▁unit ▁operations ▁around ▁the ▁Mat an ik au ▁Valley . ▁ ▁The ▁first ▁U . S . ▁Marine ▁operation ▁against ▁Japanese ▁forces ▁west ▁of ▁the ▁Mat an ik au , ▁conducted ▁between ▁ 2 3 ▁and ▁ 2 7 ▁September ▁ 1 9 4 2 ▁by ▁elements ▁of ▁three ▁U . S . ▁Marine ▁batt al ions , ▁was ▁rep uls ed ▁by