Mount and Blade Warband - How to capture a friendly town?

I started a new game with Arwa trying to overthrow sultan, but at some point Khergits came and captured Shariz. Although the main Sarranid faction is at war with Khergits they never try to recapture Shariz and I am left with a hole in my territory. I am very friendly with Khergits and I don't want to go to war with them just to get Shariz. Is there any way to get Shariz for myself? My plan was to let Sarranids get it back and then I would capture it from them. I am so frustrated right now that I would use a cheat to change the ownership of Shariz to myself if such a thing is possible. I also tried using the cheat menu to make Sarranids attack Shariz, but they just walk for a second towards it and then quit. Please help.

If you're looking to conquer it for yourself, and not for another faction you can use the cheat menu to do this pretty easily. The only caveat being you'll have to besiege the city yourself as there isn't a cheat I've heard of to outright switch ownership.

First step is to enable cheats by using this these keys: ctrl + ~ and then type nocheatmenu to block the ensuing menu.

Next, initiate a siege on Shariz. After laying siege and attacking the castle use the press the keys ctrl+alt+F4 to instantly knock unconscious all enemy troops, allowing you to easily capture the castle for yourself.

Now that you own Shariz you'll likely have made most of the Khergit Khanate upset. Thankfully, cheats help here too. If you use ctrl+left click you can teleport around the map. Use this to find Khergit nobles and strike up a conversation with them. So long as cheats are enabled you should see a conversation option that says "CHEATS!". This option allows you to set their relationship value to whatever you want it, allowing you to placate them for the loss of the castle.

Now you own the castle, took no losses during the battle for it, and nobody's upset about it.