▁Unity ▁forces ▁had ▁increased ▁to ▁the ▁point ▁where ▁they ▁r ated ▁their ▁medical ▁ev acu ation ▁support . ▁Ten ▁armed ▁U H - 1 M ▁hel ic op ters ▁were ▁acquired ▁and ▁station ed ▁at ▁U d orn ▁R T AF B ; ▁ 2 6 ▁Th ai ▁pil ots ▁were ▁trained ▁to ▁fly ▁them . ▁As ▁many ▁as ▁six ▁of ▁the ▁hel ic op ters ▁would ▁fly ▁north ▁daily ▁to ▁the ▁P lain , ▁respond ing ▁to ▁the ▁call ▁sign ▁White ▁Hor se . ▁ ▁By ▁the ▁end ▁of ▁ 1 9 7 1 , ▁when ▁the ▁Vietnam ese ▁launched ▁Camp aign ▁Z , ▁the ▁Th ai ▁troops ▁in ▁L ' Ar mee ▁C land est ine ▁had ▁largely ▁replaced ▁the ▁original ▁H m ong ▁milit ia . ▁Although ▁the ▁Commun ist ▁combined ▁arms ▁assault ▁initially ▁over ran ▁six ▁Th ai ▁strong points , ▁the ▁Th ai ▁defense ▁of ▁the ▁vital ▁base ▁at ▁Long ▁T ien g ▁narrow ly ▁saved ▁the ▁Royal ists ▁from ▁losing ▁the ▁war . ▁The ▁Th ais ▁were ▁also ▁the ▁back bone ▁of ▁the ▁Operation ▁Str ength ▁I ▁and ▁Operation ▁Str ength ▁II ▁Royal ist ▁counter off ens ives ▁of ▁February ▁and ▁March ▁ 1 9 7 2 . ▁By ▁May ▁ 1 9 7 2 , ▁the ▁H m ong ▁man power ▁pool ▁was ▁so ▁dimin ished ▁that ▁a ▁C IA ▁par amil it ary ▁advis er ▁noted ▁that ▁his ▁newly ▁rec ru ited ▁batt alion ▁of ▁gu err illas ▁contained ▁over ▁ 1 0 0 ▁youth