This tactic card says something to the effect of, 'place an enemy's activation token somewhere they don't control' I believe. I am not sure what the use of this tactic is? If an army can move through an area where there is an activation token, then you're not stopping them.
Oh wait, I may have just figured out my own question. By placing an enemy's activation token in an area, you are preventing them from moving into it. The area would already be activated, so they could play a Mobilize or Conquer to get their units in there.
Does that sound correct?