When do one's forces siege?

[Courtenay]

I had thought that any time one had units outside an enemy controlled city or fort one automatically besieged it. Several times in my current game I have had a small force outside an enemy held town, and have gotten a message saying that I had besieged the town but had obtained no result. (Which is what one would expect.) On my last turn, though, I had 25000 men with 168 guns outside of Richmond (which had 17000 inside it). However, I did not get any message about a siege at all, not even that it had been unsuccessful. If I look at Richmond, though, the tooltip says that Richmond is, in fact, besieged.

Initially I thought this might be due to the fact that all my units were in defensive mode, but I replayed the turn, putting some of them in offensive mode, and that made no difference. Does the fact that all my senior leadership in the area is inactive make a difference?

Thank you.

[arsan]

Hi!

No, you can siege on defensive and with inactive leaders. Passive forces can't siege though if i recall correctly.
If the tooltip says Richmond is besieged then most surely it is!
Maybe you missed the message log's messages somehow??
Besides the "no effect" kind of messages they can also come in the "you inflicted x casualties during the siege" or you made/they repaired a breach on Richmond defenses variety". There were nothing like these??

By the way, your forces will not siege if there is still an enemy force outside the structure. You have to fight and destroy them/expel from the region before you can siege. Maybe some rescuing enemy force came around during the turn??
If you are in defensive and still don't have 95% or more MC they can come into the region in defensive and no combat will be triggered.
Cheers!

[Courtenay]

Thank you. A Confederate force outside the city is _exactly_ what happened, and I had not realized it. Seems silly of the Confederates to me. I now have exactly 95% military control of Richmond. From what you just said, if I leave my forces on defensive posture, I will fight any enemy outside of Richmond this turn?

Again, thanks.

(Now, if someone will explain to me what the Confederate Army of the Potomac is doing next to Pittsburgh, which is why I am able to siege Richmond. This turn the AotP could take Pittsburgh, but I don't think I care.)

[arsan]

Thank you. A Confederate force outside the city is _exactly_ what happened, and I had not realized it. Seems silly of the Confederates to me. I now have exactly 95% military control of Richmond. From what you just said, if I leave my forces on defensive posture, I will fight any enemy outside of Richmond this turn?

Again, thanks.

(Now, if someone will explain to me what the Confederate Army of the Potomac is doing next to Pittsburgh, which is why I am able to siege Richmond. This turn the AotP could take Pittsburgh, but I don't think I care.)

Hi!

A force that enters a region with less than 5% MC will be forced to change to offensive posture even if it was in defensive. I think it should also work for a force already inside a region, but i'm not 100% positive
If you are strong enough put your forces on offensive just in case

The Ai is too fond of deep mass raiding unfortunately Sometimes she can't control herself and goes nuts for Pittsburg or some other northern objective
Some players advise to set the AI on low aggressiveness when she plays the CSA. It seems she offers a more historical gameplay (more deffnsive but not really that passive!)

Probably they will head back to Richmond now that your are sieging it.
Cheers!