@IW You can split a group just by getting the relevant loons to join another group. If you want a loon to be temporarily groupless, use
[loon1] join grpNull
Syntax not guaranteed, as usual.
@Quantum Jelly, sure, no probs.
First of all, create your group of M113 crew/dismounts who are to be the captives. In the init field of the group leader write
"_x setCaptive true" forEach units group this; Prisoners = group this
That will prevent the Soviets from shooting at them, and will also name the group which will come in handy later.
Create a rescue group, with the player as the leader. In the init field of the leader write
Rescuers = group this
Now create a trigger over the M113 area. Go into Groups mode (F2) and drag a line from the trigger to the leader of the rescue squad. Look in the trigger's Activation box, you will find new options. Select "Leader present". That means that the trigger will activate when the leader of that group - which is the player - is in the trigger area.
Now, in the On activation field of the trigger, write this
"_x setCaptive false" forEach units Prisoners; "[_x] join Rescuers" forEach units Prisoners
Syntax is not guaranteed, you must check all of these commands in the Command Reference in the Editors Depot.
Assuming the syntax is correct, that should make things work out as you planned.
Keywords, which will hopefully make this post easy to find in the future for people searching for this kind of stuff.
captive
prisoner
POW
join