As the invasion progresses the Aliens will begin to construct hidden underground bases on Earth, during the bases construction intense UFO activity will be present transporting supplies and personnel to and from the base site. As long as the Alien base remains operational it will continually increase panic in the region it is in and eventually cause the region to abandon the Xenonauts project, as well as increase the Alien Ticker at a constant rate.

Another note is that as the invasion progresses the Alien bases will eventually increase in size, making destroying the bases significantly harder, but increasing the potential rewards.

It should also be noted that Alien Bases can hold some of the largest Alien forces the player will fight against.

In-game BriefingEdit

Drop-ship (Drop-ship Name) is approaching (Alien Base designation). Our strike team is preparing to breach the access tunnels and launch a ground assault on the alien installation.

Elimination of all alien units in the installation will allow us to capture the maximum amount of recoverable technology and is the best-case scenario. Alternatively, if we can locate and destroy the base power cores, we will be able to evacuate our troops without clearing the base. We would recover no technology in that instance, but the alien base would still be destroyed.

Expect large numbers of heavily-armed enemies in the base, so be careful. Good luck, commander.


  1. Eliminate all Alien forces


  1. Destroy the Bases Power Generator.
  2. Evacuate all surviving personnel. (Failure here will still result in base destruction)

Alien Base PurposeEdit

A functional Alien Base provides two benefits to the Aliens.

  1. It constantly lowers the regions financial contributions to the Xenonauts project, if left operational it would eventually force the region to abandon the project.
  2. Further raising the Alien Ticker Rate, meaning the invasion will advance faster than if the base was not established.

Either way, a Alien Base should be removed as soon as possible.

Locating an Alien BaseEdit

There are a only a couple ways to discover a base or know when a base is in a region of the map.

  1. Randomly discovered by a Xenonaut agent. The game has a chance to just tell you when agents discovered a base.
  2. Friendly fly overs. Every aircraft has its own small radar attached and will discover a base if it flies over or near enemy base.
  3. Losing a lot of Money from a region. You will notice you are losing money in regions usually not covered in your radar.  The base brings in more ships to supply itself and launches ships to disrupt the region therefore causing the loss.

Base SizesEdit

As a base's size increases, the amount of Aliens on base slightly increases as well as far more deadly ranks of enemies being on base.

  • Small base(alien outpost)
  • Medium Base(alien base)
  • Large Base(alien fortress)

Control Room and Power GeneratorEdit

All Alien Bases house a Control Room and Power Generator Room.

The Control Room is the brain of the base, the bases' commanders (Officers, Leaders and Praetors) all reside in here. It will be the most heavily defended area of the base, however if all the Aliens in this room are removed and a soldier is occupying it, the entire base will be revealed as your men gain access to the base's security cameras. This of course makes it significantly easier to hunt down any remaining aliens.

The Power Generator is the heart of the base, destroying the Power Generator will destroy the base, and ties in with the alternative win condition. If you do not believe you have the man power to eliminate all of the base's occupants, or you simply have little reason to expend the manpower to take over the base, then destruction of the power generator will result in the base being destroyed, and evacuation being available.

A bases Power Generator is closer to the base entrance than the Control Room. Making it easier to simply destroy the base than capture it.

Base ComplementEdit

Alien Outpost Alien Base Alien Fortress
Rank Ceasan Sebillian  Andron  Ceasan Sebillian Andron  Ceasan Sebillian Andron
Non-Combatant 2 2 - 1 - - 1 1 -
Guard - - 2 - - - - - -
Soldier 7 9 8 - - - - - -
Warrior - - - 11 11 11 - - -
Elite - - - - - - 15 12 11
Officer 1 1 1 - - 1 - - 3
Psion 1 - - - - - - - -
Leader - - - 1 1 - 1 3 -
Other 2 2 2 6 6 3 6 5 5
Preator - - - - - - 1 1 1
Total 13 14 13 19 18 15 24 22 20


  • In the original X-COM a strategy/exploit was to keep an Alien base operational and to continually attack it, kill most units in the base and steal everything not bolted down, rinse and repeat, as well as to down and raid incoming supply ships. In order to make this an ineffective tactic, Goldhawk have made it so that Xenonaut troops cannot evacuate until the power core of the Alien Base is destroyed, while destroying the core will destroy the base as well.