Back to agent actions for a moment.

Any 'military sabotage' action by any agent against any army has the reduced movement effect on success. Not sure about the re-inforcement one, that may be champion specific. If you critically succeed then the army cannot move at all. THe flaw is that not only does it not tell you this anywhere useful (tooltip over the army effects is the only place I have found it) but it doesn't tell you whether your succes was normal or critical in your own agent success screen. Sigh.