so the guy who blew the horn (and other men) at the seige of Winterfell wasnt Winterfell forces?
What happened to the 200 Winterfell men that was sent to out on Theon's rouse?
They were mostly Bolton men, one of the many noble northern houses that serve under the Starks (Roose Bolton, the current Bolton Lord, is currently holding Harrenhal in the Riverlands, where he has Jaime and Brienne captive)
Basically they took Winterfell from Theon and are currently holding it, and keeping Theon captive, likely in the Bolton seat at the Dreadfort
meanwhile the Ironmen are holding Moat Cailin, which is surrounded by difficult terrain (supposed to be swamps and shit) and thus control the only reliable over-land pass and of course the Ironmen also likely have the most powerful remaining navy, especially since Stannis' fleet was largely destroyed by wildfire in the Battle of the Blackwater at King's Landing. So basically it was never the plan to take Winterfell directly, what Balon Greyjoy intended was to cut off the north completely at the neck and essentially hold siege to the entire north, raiding and pillaging all the other cities and towns in a guerrilla campaign while the majority of Robb's forces are trapped in the south. So basically Theon fucked up pretty big.
bigger map: