- "Warwolf, we need all the transports. If one goes down, then our wounded will die as well."
- ― Belyi Base Tower
Siege is the ninth mission in Ace Combat: Assault Horizon.
Transport flight "Sova Squadron" is preparing to provide Belyi Base with doctors and medicine for their wounded, but are unable to land due to NRF air and ground assaults on the base. Colonel Bishop and Guts send the rest of Warwolf back to refuel, while Molot provides Sova with cover. Several ground units and Su-27, Su-34, and Su-25 aircraft have already breached the base perimeter and must be destroyed immediately.
After dealing with them, Warwolf is forced to land at the base in order to refuel. The NRF has already launched a second wave of attacks by the time they take off, and the transport planes must be protected from the enemy fighters. The mission is complete when the final wave of ground forces has been eliminated.
- Due to the speed at which Sova 1 is attacked after the player takes off, the mission is not failed if it is shot down. However, getting Sova 1 to land safely results in earning the achievement Smooth Flight.
- The name given to the base with an error. The correct name of the base is Belaya (Belaya base, База Белая.) which means White Base.
- Belyi Base and the mission's background music title (White Devil) might be a direct reference to Mobile Suit Gundam. White Base is the name of the titular warship from the original series whereas White Devil is the nickname for the Gundam and its pilot Amuro Ray himself.