Yeah, I think to take it I'll need two good armies, probably with a few of the better armed Celtic mercenaries. I'll have to attack the city and the roving army in quick succession. If I can do that, I can win the province.

I completely underestimated the power of Celtic axemen. They looked conspicuously like construction workers.

EDIT:

Also, the Baltic spearmen have green hair in my game. :P