Help: Can't sally forth

So my army is besieged by the British. If I don't attack them, my army will surrender. So I decided to attack them, but then I found that I can't!

When I selected the army in the city, they don't allow me to attack the besieging British army. That is the first time my city is under siege.

I have never seen this before on previous total war game. How do I sally forth so that i can defeat them? Is there some special move I have to make, some button hidden?

If I leave it there, my major army would fall and i have to rebuild again!

I wonder if this is one of those Zone of Control problems. There seems to be an issue of naval ZoC affecting land troops and making them unable to move. Is there a british ship so near its ZoC extends to your city? Try getting rid of it.

Select every unit when you tell them to attack/sally. For some reason when you don't, it doesn't let you attack.

known bug (i've posted it a couple weeks ago in the bug thread). Only workaround is to bring a unit that is not besieged and attack the besieging army.

Damn it
That was a lone army.....in the America....like a single expedition.
Guess I will lose this experienced army

So never get besieged! Thanks guys.
Hope they would patch it.......

It has something to do with moving out of a city and attacking or merging with a stack next to the city.

I cannot merge units within a city with a stack right outside it, and I cannot sally forth either.