ension ▁was ▁replaced ▁by ▁the ▁superior ▁vertical ▁vol ute ▁system ▁in ▁the ▁T 2 E 1 ▁series ▁of ▁ 1 9 3 5 . ▁This ▁was ▁put ▁into ▁production ▁with ▁minor ▁modifications ▁as ▁the ▁M 2 A 1 ▁in ▁ 1 9 3 6 , ▁with ▁ten ▁produced . ▁The ▁main ▁pre - war ▁version ▁was ▁the ▁M 2 A 2 , ▁with ▁ 2 3 9 ▁produced , ▁becoming ▁the ▁main ▁tank ▁in ▁the ▁US ▁Army ▁inf antry ▁units ▁in ▁the ▁inter war ▁period . ▁The ▁Spanish ▁Civil ▁War ▁showed ▁that ▁t anks ▁armed ▁only ▁with ▁machine ▁guns ▁were ▁in effect ive . ▁This ▁led ▁to ▁the ▁M 2 A 4 ▁with ▁a ▁ 3 7   mm ▁gun ▁as ▁the ▁main ▁arm ament . ▁A ▁total ▁of ▁ 3 7 5 ▁were ▁delivered , ▁the ▁last ▁ten ▁as ▁late ▁as ▁April ▁ 1 9 4 2 . ▁ ▁Its ▁only ▁combat ▁use ▁in ▁American ▁units ▁was ▁with ▁the ▁US ▁Marine ▁Corps ▁ 1 st ▁T ank ▁Battalion , ▁during ▁the ▁Pacific ▁War , ▁in ▁ 1 9 4 2 . ▁However , ▁it ▁is ▁believed ▁that ▁M 2 A 4 s ▁served ▁in ▁Bur ma ▁and ▁India ▁with ▁the ▁British ▁ 7 th ▁H uss ars ▁and ▁ 2 nd ▁Royal ▁T ank ▁Regiment ▁during ▁their ▁engag ements ▁with ▁the ▁Imperial ▁Japanese ▁Army ' s ▁ 1 4 th ▁T ank ▁Regiment . ▁▁ ▁On ▁the ▁Western ▁front ▁the ▁tank ▁was ▁used ▁in ▁many ▁combat ▁operations ▁from ▁August ▁ 1 9