If they were trying to be super sneaky about it, they wouldn't have kept the fething war status...
Well, there's that. But imagine the surprise when a fleet of Zonasan vessels shows up in the harbor filled with troops! I guess in all technicality, that'd be something never before seen in the Far East by any noble, so its bound to surprise someone the first time it happens.
"What do you mean they're coming by sea? That's impossible and stupid!"
"But, but, but...they're in the harbor, my lord!"
"I said
impossible AND
stupid!"
Then comes the surprise arrow volley and the influx of troops. See, all very surprising.