Download the offline Fortress Under Siege XAP | APPX | APPXBUNDLE files for Windows 10 Mobile | Windows Phone . You can download FREE to install manually now. Windows Việt only share the original XAP | APPX | APPXBUNDLE installer for apps and games. All the Windows 10 Mobile | Windows Phone apps & games here are free for home or personal use ONLY. Fortress Under Siege is the property and trademark from the developer of it, all rights reserved. Please do not reupload to Microsoft Store.