Whatever you want to call it, Constantinople is going down, down, down, don't mess around. A real nice city for Leonidas -- possibly better than his own capital, in all honesty. With Byzantine archers all uselessly embarked and thereby in the Danger Zone, Leonidas may well have designs beyond Constantinople as well.
From the north, Polish traders ply the wastes of Carpathia, will they return news of the Byzantine feeding frenzy in time to give Kasimir the notion of extending his southerly holdings? And in the east, Armenia's army does not look capable of meaningful intervention -- yet. They have only just declared war, though, so it remains to be seen how many forces are going to shuflle back towards Asia Minor. Tiridates has historically beligerent rivals on many sides.
You have got to hand it to Sparta; their uiniques always had them primed for early conquest; even after whiffing against Rome and Poland, Leonidas finally blundered into the right patsy and is pressing it all the way home.