Problem If you were attempting to take over an O'Neill Cylinder without destroying it or the majority of its inhabitants/ecology how would you go about it? What benefits or detriments to an attacking or defending force would the gravity and the cylinder shape of the land have to a fighting force?
Assumptions The tech required to make an OC isn't too far off what we have now and so in terms of tech you can expect it to be similar somewhat to the those living onboard the Elysium (from the film of the same name).
The OC your attacking is of strategic or cultural importance and you intend to take it over and replace its government with your own whilst doing minimal damage to its contents.
Its current government has dug in with its own combat forces so you should expect some resistance, as in they expect you to make a move to take the cylinder.
Question What would combat look like inside an O'Neill Cylinder?