I was able to get this scenario to work properly, but had to use the allowfleeing command.
It seems that by setting the allowfleeing to 1 when the group had been reduced the proper ammount they would disengage and beat-feet outa the firefight.
I set this up on the desert island, placed a platoon of soviets, set their allowfleeing to 0, and had them move into position. At the opposite end of the island I placed a platoon of West soldiers, set their allowfleeing to 0, named the group plt1 and gave them a HOLD waypoint near the soviet waypoint, and a move way point some distance away from the battfield.
I created a trigger of type switch and put in the condition field count units plt1 < 8 and in the activation field "_x allowfleeing 1" foreach units plt1. Sync this with the Move WP.