▁Th ai ▁volunte ers ▁without ▁prior ▁military ▁training ▁were ▁accepted ▁for ▁service ▁in ▁La os . ▁The ▁Unity ▁force ▁bal lo oned ▁from ▁a ▁strength ▁of ▁ 1 4 , 0 2 8 ▁in ▁June ▁to ▁ 2 1 , 4 1 3 ▁in ▁September . ▁ ▁Military ▁Region ▁ 4 ▁ ▁On ▁ 1 5 ▁December ▁ 1 9 7 0 , ▁BC ▁ 6 0 1 ▁and ▁BC ▁ 6 0 2 ▁were ▁hel il ift ed ▁to ▁the ▁abandoned ▁village ▁of ▁Hou ei ▁S ai , ▁La os ▁to ▁begin ▁military ▁operations ▁in ▁Military ▁Region ▁ 4 . ▁Oper ating ▁under ▁the ▁code ▁name ▁V ira kom , ▁they ▁were ▁so ▁successful ▁that ▁C IA ▁case ▁officers , ▁not ing ▁the ▁contrast ▁with ▁the ▁Kh mer ▁troops ▁of ▁Project ▁Co pper , ▁thought ▁the ▁Th ais ▁might ▁re capt ure ▁the ▁Bol oven ▁Pl ate au ▁for ▁them . ▁ ▁On ▁ 2 7 ▁July ▁ 1 9 7 1 , ▁Unity ▁troops ▁were ▁committed ▁to ▁Operation ▁Say as ila ▁in ▁a ▁drive ▁to ▁re capt ure ▁the ▁vital ▁air ▁strip ▁at ▁Sal avan . ▁Later ▁in ▁ 1 9 7 1 , ▁they ▁would ▁particip ate ▁in ▁similar ▁off ens ives ▁in ▁Operation ▁Bed rock ▁and ▁Operation ▁Th ao ▁La . ▁By ▁December , ▁the ▁P AV N ▁was ▁press uring ▁the ▁Royal ists ▁in ▁operations ▁designed ▁to ▁push ▁them ▁away ▁from ▁the ▁Ho ▁Chi ▁Min h ▁Tra il ▁and ▁backwards ▁toward ▁Th ailand . ▁ ▁By ▁June ▁