Alien Base

One of the ways in which the threat to humanity manifests is the construction of Alien Bases on Earth. These bases are the first step in the attempt to control the world, and as such are a significant threat that undermines X-COMs mission.

Alien Bases add significantly to the Alien score when they are constructed and between that and the much higher UFO activity present will have neighbouring countries in particular very agigated, possibly leading to them reducing or withdrawing funding. As such Alien Bases in key areas will need to be dealt with somehow, while Bases in remote locations might well not be so critical to target for action immediately.

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. See: Alien Missions
• 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.
• Check your graphs for UFO activity by region. A spike of UFO activity in a given region probably indicates the construction of a base there.
• Alien bases are numbered by generation, not by detection. If you already have destroyed 3 alien bases before discovering "alien base 5" you should continue your search to find number 4.

Goal

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. Specifically, you must destroy all 16 sections of the 4 purple octagonal tables (normally these are UFO Navigations). A single Blaster Bomb to the upper level will usually set off a chain reaction: if you hear 16 explosions in a row, you're all set.

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.

If you do abort the mission, be sure to move all your troops onto the green tiles in the "exit areas" on the upper level. Any troops not on a green tile (including those on the red lift tiles in the exit rooms) will be counted as MIA.

It is often much easier to infiltrate the Command Center by shooting through its walls (and ceiling) than by entering it via its doors and access lift. See Destroying Terrain#UFO walls for more details.

Recoverable Components

The components that can be recovered from an alien base varies, dependent on what modules are used in its layout (see Alien Base Terrain). Most of the recovery value from an alien base assault will come from recovered alien armaments. See UFO Recovery Values#Alien Base Assaults for more details.

Alien Deployment

Rank	Beg./Exp.	Vet./Gen.	Super.
Soldiers	5-9	6-10	7-11
Navigators	1	1	2
Medics	1	1	1
Engineers	1	1	2
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 storage room with power units. Destroy the power units 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. Consider grabbing a few alien equipment on your retreat to replenish any spent equipment during the raid, and perhaps if you are lucky enough to knock out a high ranking alien, drag it back to the entrance to have it abducted.

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 at least one alien alive in the base.

One tip is to knock out an alien, bring it somewhere safe where you can watch over it (such as the small storage rooms with the small grav-lift), then revive it with a Medi-Kit. Proceed to wipe out the rest of the aliens, but do not damage the command consoles in the command centre. As soon as the base is neutralized, initiate a recovery mission and gather as much equipment (and corpses, if you're really stretched for cash) in the green entrance pads before aborting the mission. Though this may seem time consuming, it does allow you to reap the rewards of a normal successful mission.

The mission will be counted as a technical failure, but that's nothing to worry about, as the activity points, loot and experience will tell you otherwise.

Many (or most?) alien bases will not have power units, or any Elerium. Recent research has shown that attacking a base's Supply Ships is likely to be more profitable (and less dangerous) than attacking the base itself, and a more reliable source of Elerium. See UFO Recovery Values#Alien Base Assaults for more details.

Alien Base Tactics

Camper Strategy

The "camper" strategy exploits two quirks of the game: aliens cannot fire conventional weapons up or down through lift tiles, and will fall prey to the "Vertical Waypoint Bug". When the aliens attempt to fire Blaster Bombs up the lift shaft, this bug will cause the bomb to travel south, not up, keeping your troops safe on the upper level. The vertical waypont bug only exists in the "Collector's Edition" (Windows) version of X-COM; the camper strategy cannot be safely used in any other version of the game.

To use the camper strategy, have all your troops retreat to the upper level of the access lifts (the green-tiled rooms). Position a soldier on each square of the lift on the upper level so aliens cannot use the lift to come up (this requires a minimum of 8 soldiers or 2 HWPs). The simplest thing to do is then wait until turn 20+, when all the aliens will exit their own encampments and mass on the lift squares below you. You can then shoot them. To reduce the chance of your troops accidentally shooting each other, have them only shoot at aliens located directly beneath them.

Camper tactics can also be used on other lifts found within an alien base, with varying degrees of effectiveness. Rooms which have only one entrance (including the control room) are best, as you do not have to guard your back. However, these rooms are dangerous to approach and clear of aliens in the first place.

Camping cannot be used in Sectoid or Ethereal bases unless your troops have extremely high Psi Strength and are able to completely withstand Psionic attacks (especially Mind Control).

Camp and Scout

Instead of waiting, you can also choose to send a scout down the lift every turn. Have the scout turn in place to survey the immediate area; if any aliens are spotted, you can send other troops down to shoot or grenade them. Depending on how many TUs the alien(s) have left, your scout may get fired upon when descending the lift, or the other soldiers when firing upon the aliens. Dropping a Smoke Grenade in the center of the lower lift room can reduce the number of aliens that can see your troops while they scout.

If the coast is clear, you may wish to have soldiers retrieve nearby corpses or alien gear, so as to prevent them from being destroyed if a Blaster Bomb is set off in the room. You may come under fire from aliens that were not initially visible, however, and it is easy to miscalculate how many TUs are needed to retrieve items and return to the upper room.

Camp and Grab

After killing several aliens, most of the surviving aliens will panic. If you wish to use camper tactics during a "Smash and Grab" mission, it is easy to approach one of these survivors, stun him, drag him up the lift and use a Medi-Kit to revive him (don't use a Terror Unit, as they have in-built weapons). You can then kill any remaining aliens you see and collect Elerium and whatever other goodies you wish.

Mind Control Strategy

Once you have a large number of psi-talented troops, it is easy to win all combats with ease: Mind Control one alien, have it seek out others, then Mind Control any aliens it spots, and have them explore further. Disarm them, then line them up for slaughter.

Notes

• 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.
• 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. They will have their associated terror units there.
• 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.
• Don't linger long in the rooms beneath the access lifts, and stay spread out at all times. There WILL be aliens with blaster bombs here, and they will be happy to use them on any clusters of your troops.
• If you are trying to capture a Commander, be aware that before entering the inner door of the command center, if the commander is not killed or incapacitated before the end of the turn where the door is opened, he may fire his blaster launcher and kill himself and most of the aliens in the command center accidentally.
• Also be aware that bases staffed by Mutons will never have a Commander; Mutons can only be Soldiers, Engineers, or Navigators.
• Feel free to throw explosives around to open up the terrain, especially in those garden areas. It's your enemy's base, after all.

See Also

Alien Base Terrain