Alien Base Assault

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XCom operatives have gained entrance to an alien base. The control centre must be destroyed to render the base inoperative. The Mission will terminate when all enemies are eliminated.

Locating an Alien Base

Alien bases do not show up on the Geoscape by default. They are hidden until you find them. To locate one, an X-Com craft must patrol in its vicinity for a short time. Also, X-Com agents may report a base location to you at the beginning of the month, but that shouldn't be relied upon.

There are several clues that indicate the presence of an alien base. A large UFO performing an "Alien Base" mission may indicate the creation of a base, or a preliminary scouting mission. Several UFOS running alien base missions simultaneously indicate the construction of a base, and the base may be built even if you interdict all of those UFOs. An "Alien Supply" mission will always land directly on top of a base; patrol the location until you find it. For each nation that the aliens enter a pact with, they will also build a base somewhere on that nation's continent-- but not necessarily within that nation's borders.


Destroying the contents of the room on the second floor of the Command Center renders the base destroyed for all intents of a base assault. If you abort the mission after destroying the command center, the base will be destroyed. However, The mission will not end until you abort it or kill every alien in the base-- the latter is of course to be preferred.

Alien Deployment

Rank       Beg./Exp.  Vet./Gen.    Super.
----       ---------  ---------    ------
Soldiers      5-9        6-10       7-11
Navigators     1          1          2
Engineers      1          1          2
Medics         1          1          1
Leaders        2          3          4
Commanders     1          1          1
Terrorists    1-3        3-5        5-7

Totals       12-18      16-22      22-28

Smash And Grab

Alien bases can be a very quick and dirty (dangerous) way to get Elerium, using what we call the "smash and grab" mission. Raid them by seeking out the room with red fuel pods. Destroy the pods without using explosives, and pick up the purple elerium canisters that were underneath. Boogie back to the entry lift, and abort the mission. You get the elerium and the base is not destroyed. This means you can raid as often as you dare.

If you want to do repeated Smash And Grabs on the same base, you must not destroy the base Control Center, and you must leave some aliens alive in the base.


  • Somebody turned the lights out. Alien bases start dim and remain dim, so bring electroflares.
  • Remember those proximity grenades; you can't guard every intersection.
  • Terror units will be in the area.
  • The alien base will be staffed by the same variety of aliens that ran the "alien base" UFO mission that set the base up, and the aliens that run the "alien supply" missions to that base. See Alien Missions For more detail.
  • Alien bases populated with Snakemen deserve special caution. The high mobility of the Chryssalid makes it especially dangerous here-- it can run around three corners and still have enough time to infect your troops.
  • The Alien Base Commander and a couple leaders will usually- but not always- be hanging around the Control Center. Expect at least some of them to have blaster bombs.
  • Alien Engineers hang out around the Storage Loft sections. many of them will be armed with blasters as well.

See Also

Alien Base Terrain