maybe you shouldnt use a script. You could put in their init field:
this setbehaviour "CARELESS"; this switchmove "EffectStandSitDown"
this would make them not move and stay in the sitting down position. In the trigger to make them get back up and to fight the incoming US man, just put in the On Activation of the trigger:
unitname setbehaviour "COMBAT"
unitname is the name of the russian soldier name around the fire
hope this helps