It depends on what their orders were, most often not much happens. I have moved a Carthaginian FM to my Italy in 221 BC as the 2nd Punic warmed up and now attacked him twice in Italy. Apart from defending he just wanders aimlessly around, so I think I will drop history and just expand slowly (the AI already has despite my best efforts at helping AS by console-creating money and units it cannot stop The Yellow Death).