Operation denial - bug?

[epower]

Can't seem to operate any units into the vicinity of Wuhan even though I've controlled the area for a few turns and there's a clear, partisan-free rail connection all the way thru. In the screenshot below I've selected a nearby garrison unit but the same thing happens for any unit in mainland China with a operable rail connection. Not seen this limitation before so I thought I'd run it up the flagpole. Am I missing something?

Posted this in the WiE forum by mistake, so moved it here. Blast that small font!

[Hubert Cater]

Valid cities need to have a strength >= 5 in order to operate to them. For example, this is useful when implementing a Strategic Bombing campaign whereby knocking out key cities can have a detrimental chain reaction effect upon the ability of your opponent to effectively move their forces around.

[epower]

Devil's in the details I'll ask my assault troops to be a bit less destructive next time they take a city.
I haven't done a strategic bombing campaign yet but I will definitely remember this when the time comes.

Thanks for clarifying that Hubert.