0 0 . ▁The ▁ 1 9 6 9 ▁N ixon ▁Do ctrine ' s ▁flexible ▁response ▁strategy ▁required ▁a ▁non - n uc lear ▁answer ▁to ▁this ▁dispar ity . ▁The ▁Ans bach ▁Test s ▁suggested ▁this ▁could ▁be ▁a ▁force ▁of ▁a ▁few ▁hundred ▁attack ▁hel ic op ters , ▁which ▁could ▁be ▁purchased ▁and ▁deployed ▁for ▁a ▁fraction ▁of ▁the ▁cost ▁of ▁an ▁equivalent ▁tank ▁fleet . ▁ ▁This ▁spark ed ▁off ▁one ▁of ▁the ▁most ▁inten se ▁deb ates ▁in ▁the ▁long ▁history ▁of ▁tank - vers us - ant it ank ▁arguments . ▁US ▁Army ▁doctrine ▁to ▁that ▁point ▁was ▁that ▁" the ▁best ▁defense ▁against ▁a ▁tank ▁is ▁another ▁tank ," ▁but ▁pro ponents ▁of ▁the ▁hel ic opter ▁claimed ▁that ▁" the ▁attack ▁hel ic opter ▁represents ▁the ▁final ▁resolution ▁of ▁the ▁tank - ant it ank ▁debate ". ▁In ▁the ▁years ▁following ▁the ▁tests , ▁the ▁Army ▁began ▁converting ▁their ▁Cob ras ▁to ▁the ▁eight - TO W ▁A H - 1 S ▁model ▁and ▁changing ▁their ▁role ▁to ▁be ▁primarily ▁anti - t ank ▁vehicles . ▁ ▁Background ▁Ans bach ▁was ▁carried ▁out ▁as ▁a ▁result ▁of ▁several ▁previous ▁events ▁and ▁studies ▁stretch ing ▁out ▁over ▁a ▁de cade . ▁Among ▁them ▁were ▁the ▁ 1 9 6 0 ▁Rog ers ▁Board ▁recommend ations ▁on ▁Army ▁aircraft ▁development , ▁which ▁had ▁comments ▁about ▁the ▁development ▁of ▁the ▁hel ic opter ▁as ▁a ▁combat ▁vehicle . ▁In ▁April ▁ 1 9 6 2 , ▁Robert