XCOM: Enemy Unknown guide - squad builds, ET tactics, base-building strategy and more

Tom Hatfield


XCOM is back! And as you've probably realised from our XCOM review , it's brilliant, capturing everything we loved about the original game, but with lots of clever modern ideas thrown into the mix. The new game is different enough from the old one that even X-Com veterans could do with a few tips, never mind rookies. Thankfully I'm here to help. After spending many, many hours in the game, I've assembled this guide, collecting all the best tips I can offer to help you deal with the alien menace. What's more, you can also find Chris' video guide to surviving Ironman mode embedded above.

But, before we get started, here are some other XCOM tips you might be interested in:

How to recruit hero characters.

How to force the game to use 1080p cinematics.

The dev's own tips for taking down early-game ETs .

Building your Base

Restart after the tutorial – The XCOM tutorial is very handy for learning the basics of the game, but it's also very linear. Starting again after you've finished it will give you the freedom to plan your base how you like, and ensure you don't lose three men on the first mission.

Win the space race – If I could only give you one tip, it would be this. Build satellites. There are no second bases in Enemy Unknown, so it's vital that you launch satellites and buy interceptors in order to spot UFOs around the Earth. Secondly, each satellite you launch will provide extra resources and calm the nation it's launched over. Thirdly, when you complete the satellite coverage of a continent you'll get the same bonus you would if you put your base there. This is why it's pointless to set up in South America, since you'll only need two satellites to do the same job as a whole base.

XCOM guide

Mine for steam – Thermal generators are way better than regular power generators, but they can only be built on steam vents. So the best way to produce power is to quickly mine down to the steam, build a thermal generator and then surround it with regular generators for the adjacency bonus.

Engineers are better than Scientists – Every item in Enemy Unknown requires a minimum number of engineers to build. Conversely, a single scientist can research everything in the game, extra ones just make it go faster. So if the game offers you a choice between engineers and scientists, go for the engineers. I've never built a single laboratory while playing this game, I've just never needed the speed boost. Workshops, on the other hand are very useful, granting you access to more items and refunding your resources.

Weapons versus armour – This one is a tough call. Armour is generally faster to research, as there are several different guns for each class, while one suit of armour fits all. If you've got veterans to protect, I recommend prioritising armour. If you're dealing with a squad of rookies (often the case if you're an iron man player) then I'd go for weapons instead. The upgraded rifles make noobs far more likely to actually kill something.

Train your officers – Building an officer training school gives you access to some powerful upgrades. You can improve experience gain, increase your squad size and make your soldiers more likely to survive. All essential if you're going to develop a veteran squad.

XCOM guide

Combat Tips

Keep your ears open – As you move across the battlefield, you might notice sound waves coming from off screen. These are little clues as to where the aliens on the map are positioned, Firaxis' solution to all those old X-Com missions which ended with a half hour search for the final alien. As an extra bonus, the sound clip that plays at this point hints at what kind of alien you'll find. Stomping and Darth Vader breathing means Mutons, while skittering insectiod movement means Chyssalids.

Overwatch is key – Overwatch is XCOM's version of X-Com's reaction fire, and it's one of the most powerful weapons you have at your disposal in the field. Always have at least one or two men on overwatch to cover the rest of the squad before moving or ending your turn. The only reason not to have someone on overwatch is if you've already spotted the enemy and are busy filling him full of lasery death.

Exploit enemy movement – Whenever an enemy spots you, they are allowed one move action. Ranged units will panic and dash for cover, while melee units charge forwards. You can exploit this movement by putting your whole team on overwatch before moving the last man forward, this way if you provoke an enemy, they'll run right into your firing arcs and get horribly slaughtered.

Use stealth – That enemy movement I spoke about? It happens when they spot you, not when you spot them. This means that by using a Ghost Suit's invisibility, or the Sniper's Battle Scanner you can spot the aliens while they're still clustered together and they won't react until you've dropped a grenade right in the middle of them.

Make your own door – Back in the original X-Com, opening a door was suicide. Things aren't as bad these days, since you can now fire from cover at either side of the door. Still you can often surprise the enemy by simply blowing a hole in the wall with a grenade and making your own entrance.

Exploit explosions - Blowing up a UFO power source does some serious damage, but if you do it, you won't be able to salvage it at the end of the mission. However if you're using thermal power, you don't actually need that many, so you can happily use it to magnify take out the enemy. The same trick also works with cars, which is why you should never stand next to a burning one.

Next: Your squad and how to build them.



The Heavy has two main weapons, a big machine gun and a rocket launcher. He excels at laying down suppressive fire and destroying cover, in addition to dealing big one shot damage.

Recommended perks:

Burst of Steel – Firing in XCOM usually means the end of your soldier's turn, but with Burst of Steel if you stand still and fire you can take a second action. That action can be to move, reload, go into overwatch or even fire twice for maximum dakka.

Suppression – Suppressing fire is a special kind of shot. It doesn't do any damage, but it does reduce aim, destroy cover, and grant you a reaction shot if your target moves. It's a very useful weapon in your armoury, especially if the enemy is stupid enough to hide behind something explosive.

H.E.A.T. rounds – Doubles your damage against robotic enemies. This ability may not seem useful when you first get access to it, but two of the strongest enemies in the game, Cyberdiscs and Sectopods, are robotic, and this really helps you deal with them.


Assaults are the guys who get up close and shotgun the enemy in the face. Their signature move is Run and Gun, which lets them move twice and still fire or go on overwatch.

Recommended perks:

Lightning Reflexes – One of my favourite perks in the game. Lightning Reflexes forces the first overwatch shot against your soldier to miss. This not only keeps him alive and lets him close in on the enemy, but can be used to clear the way for the rest of your soldiers.

Close Quarters Fighting – Grants a reaction shot against anyone who approaches within four squares of the assault soldier. I've lost count of the number of times this has saved my ass from being injected with Chyssalid eggs.

Rapid Fire – Fires a double shot, but at reduced accuracy. At close range this can be devastating, and if you use a pistol, it works at a distance too. There's also a second reason to get it, it's counterpart, Flush, is far less useful, and often doesn't seem to work at all.


Snipers can do massive damage at range, capable of taking out even tough enemies like Mutons with a single shot. But they can't move and shoot with a sniper rifle, and struggle to hit enemies up close.

Recommended perks:

Snap Shot – Lets you move and fire with a sniper rifle at reduced accuracy. The choice between this and Squad Sight (shoot anyone any soldier can see) is a hard one, but the latter is often foiled by inconvenient walls, while Snap Shot lets your sniper keep pace with the rest of the squad and still be useful.

Battle Scanner – An overlooked skill, since it's one of the few Sniper abilities that doesn't involve shooting people. Tossing this scanner reveals part of the battlefield, including any enemies nearby. However it does so without alerting the enemies to your presence, meaning they don't scramble for cover.

Opportunist – Removes the accuracy penalty for overwatch attacks. This lets a Sniper climb to high ground and cover the entire squad with ease. Opportunist helps compensate for the aiming penalty for Snap Shot, or pull off some amazing trick shots with Squad Sight.


Supports are one of the most versatile classes in the game. They use standard rifles and can toss smoke grenades, but their main draw is their superb medic abilties. I usually take two Supports per squad, they're that useful.

Recommended perks:

Field Medic – This incredibly useful ability allows you to get three uses from every medpack, turning your support into a roving medic. It's an absolute must have, the best way to keep your squad on their feet throughout the mission.

Revive – The second strong medic ability in the support tree. This one means that critically injured squad members can be revived instead of merely stabilised, because nothing can stop an XCOM soldier from kicking alien ass.

Deep Pockets – Every Support gets this ability at Major, but it's worth pointing out just how good it is. It allows you to take two inventory items instead of just one. Letting you carry a grenade or protective vest in addition to your standard medpack.

XCOM guide

Psi Ops

When a soldier is found to have psychic powers, they unlock a second, smaller skill tree. Using these powers grants you the experience to climb that tree, making your best soldiers even more potent.

Recommended perks:

Mindfray – The one ability every psychic has. It deals five damage and reduces the target's aim, willpower an mobility. It's extremely accurate over long range, kills weak aliens quickly and sets up tougher ones for other mental attacks.

Psychic Inspiration – Finally! A way to stop those weak willed rookies from panicking and shooting their pals. Psychic Inspiration removes panic and Mindfray effects and boosts willpower, a massive boost to your men's resolve.

Mind Control – The power you've finally been waiting for. Mind Control lets you pull the same tricks as Sectoid Commanders and take control of the enemy units. Sadly, your version isn't as effective as theirs. The aliens have several units that are immune to or resistant to psychic powers, and will happily shoot down their own soldiers before you can use them much. It's still incredible fun when you pull it off though, especially when paired with Mindfray to lower their defences.

Next: Your equipment and the alien menace.

XCOM guide


S.H.I.V. Units – These are small tanks that can take the place of an XCOM soldier. They can't take cover, and don't have much more health than well armoured soldier, but they do have decent weapons and (if upgraded) can use the Suppressing Fire ability. Generally speaking a S.H.I.V is better than a rookie, but inferior to a veteran soldier. Their one saving grace is immunity to mind control, making them handy for taking out psychic aliens.

Skeleton/Archangel Armour – Both of these work the same way, they give their wearers the ability to reach higher ground, either by grappling hook or by flight. They are best used by Snipers, who benefit most from increased elevation.

Ghost Armour – While Archangel Armour's function is obvious, Ghost Armour is a little more uncertain. The grappling hook and light protection fits a Sniper, but the invisibility seems more suited to Assaults. In the end I preferred it on the latter, using the grappling hook to quickly close in on enemies and drop down on them from above, Spiderman style.

Grenades – Frag Grenades do three damage to all enemies in their radius, usually less damage than merely shooting someone, but their ability to fly over cover and destroy terrain makes up for that. They're a useful tool, and it's always worth taking a couple on mission. Autopsying a Cyberdisc will let you upgrade to Alien Grenades, which do five damage, and it's well worth doing.

XCOM guide

Nano Vest/Chitin Plating – Both of these increase your health by a small amount, which useful in the early missions, but rapidly irrelevant when you have strong armour. You'll get more mileage out of Chitin Plating's secondary ability, which reducing incoming melee damage. This is a great way to protect yourself from Beserkers and Chryssalids.

S.C.O.P.E. - This offers an simple +10 bonus to aim, and also extra critical chance when upgraded. This is very useful to Snap Shot using Snipers, letting them overcome the penalty for moving and shooting. As your troops reach higher levels it becomes less useful, as their aim will be high enough already.

Medpacks – It's always worth taking a couple of Medpacks on a mission, they can restore hitpoints, cure poison and stabilise dying soldiers. Medpacks are best carried by Support soldiers, who can take several perks to enhance them. Be sure to autopsy a Thin Man as soon as possible in order to double the amount of damage you can heal.

Arc Thrower – The Arc Thrower is essential to the completion of the game, as it's the only way to stun and capture a live alien, but it's also a useful tool. It can easily take out low health enemies at short range, and the first captured alien of each type offers a research bonus. It declines in usefulness as aliens get more health, but becomes interesting again if you grab the upgrade that allows it to repair SHIV units.

Combat Drugs – Psychic powers getting you down? Why not snort the crushed bones of a Muton Beserker? Well for lots of reasons obviously, but there are positive effects too. Taking these Combat Drugs boosts your willpower and grants extra movement speed and damage resistance, making them useful for taking out psychic aliens.


Sectoids – Sectoids are weak and easy to kill, but like to scamper around and flank you. Their special 'mind link' ability allows one Sectoid to heal and buff another. If you spot this happening, aim for the Sectoid who started the link, this kills both enemies with one shot.

Thin Men – Thin Men are much like Sectoids, but quicker and more agile, able to quickly leap over obstacles. Their special ability is to spit a toxic cloud that poisons your soldiers. Be sure to avoid bunching your men up, or you'll quickly run out of medkits trying to cure them all.

Floaters – The unfortunately named Floaters are some of the more manoeuvrable enemies you'll face. Their flying abilities let them easily hop over obstacles, but can also often strand them out of cover. Occasionally they like to fly straight up in the air and drop down behind your men. Always have a man on overwatch to deal with this. Floaters will eventually be replaced by a souped up version called Heavy Floaters, which act the same but have greater health and damage.

Outsiders - Outsiders act as a sort of captain to enemy ships, having a chance to turn up in downed UFOs. They've got more health than the standard enemies you'll face around this time, and can do some nasty damage with their plasma rifles. Fortunately there's only ever one per ship, and they only appear once you enter the ship. This means the best strategy is to carefully sweep the area of all other aliens before venturing inside. One Outsider isn't a huge threat to a full squad, but triggering him in the middle of a large firefight can spell doom for inexperienced troops.

Chryssalids – Chryssalids were one of the original X-Com's most feared enemies, but they're marginally less terrifying this time around. While they retain their high speed, deadly melee and ability to turn their victims into zombies, their health is now firmly in the 'middleweight' range. Chryssalids will always rush straight at you (or a civilian) and try and engage in melee, which means that taking cover is less important than keeping your distance, and they'll almost always trigger overwatch fire.

Mutons – Mutons are essentially an extra durable ranged unit. Not as agile as Thin Men, but tougher and harder hitting. They also like to throw grenades at clusters of XCOM units to destroy their cover. Once a Muton reaches half health, it will use its Intimidate ability, triggering panic in units with low morale. It all adds up to a fearsome enemy, but there aren't really any special strategies to use beyond 'shoot them a lot'. Later in the game Muton Elites, tougher versions with larger guns, will start to appear.

Sectoid Commanders – Sectoid Commanders have more health and a stronger ranged attack than regular Sectoids, but usually eschew shooting in favour of mind controlling your men. This is very hard to deal with, especially as they often come in pairs and use Mindfray to lower the target's will before 'assuming direct control'. If this happens, kill the controlling Sectoid as quickly as possible to get your man back. The best counter to Sectoid Commanders are your SHIV units, which can't be mind controlled. Alternatively, strengthen your will with Combat Drugs or Psychic Inspiration.

Drones – Drones are fast, manoeuvrable flying enemies with low health and damage. They can be a real nuisance on Terror Missions, where they can fly around zapping civilians wily nilly. Most of the time however, they stick close to a Cyberdisc or Sectopod, using their repair abilities to restore its health. The best way to deal with a Drone is to hit the unit it's repairing with a Rocket or Alien Grenade, as the Drones will usually be taken out in the blast, while still dealing good damage to the primary target. Upgraded Arc Throwers can be used to take control of Drones, but since they're usually next to something scary, it's rarely worth it.

XCOM guide

Cyberdiscs – The first real heavyweight unit you'll face, the Cyberdisc can fly in it's closed form, or open up to deal heavy damage and throw grenades a long distance. They are also often followed by Drones who will repair any damage it takes. The Cyberdisc's weakness is it's inability to take cover, making it easy to hit, and its vulnerability to HEAT rockets. It is advisable to tackle the Cyberdisc from as long as distance as possible, reducing it's chance to flank you or throw a grenade, and taking advantage of its erratic movement.

Muton Beserkers – The Beserker is a special kind of Muton, he carries no weapons, but has a fearsome melee attack and the ability to smash straight through cover. He also has another ability that is a little more interesting, every time he gets shot, he charges forwards a few steps. This can let him close in on your soldiers very quickly, meaning you are best off hitting him with a couple of heavy shots, rather than several light ones. Clever commanders can make this extra movement work to their advantage, hitting him from distance with a sniper in order to bring him within range of an assault, or forcing him to run in circles by shooting him with several different soldiers in different positions.

Sectopods – Sectopods are some of the toughest enemies you'll ever face. These walking tanks have truly enormous amounts of health, and can do tremendous amounts of damage. A Sectopod has three kinds of attack, a powerful direct beam weapon, an indirect artillery barrage and a plasma gun which is perpetually on overwatch, even if the Sectopod has fired this turn. Thankfully they are also large and slow, allowing you to avoid their fire arcs and slowly wear them down. Use grenades to attack them from a place of safety, burn up their overwatch shots with Lightning Reflexes, and only engage them head on if you have full cover.

Ethereal – The big daddy of the alien world. The Ethereal is the most fearsome opponent you'll ever face. Like Sectoid Commanders they love to mind control your men, but they also have a couple of other nasty tricks up their sleeves. The first is a psychic storm, which deals damage in a radius and lasts for several turns. For this reason you should avoid engaging an Ethereal in tight quarters. Secondly, they deflect any shots that miss them back at the unit that fired them, meaning you should only shoot when you've got a very good chance to hit. Thankfully the deflection doesn't work on area attacks, so feel free to spam them with as many rockets and grenades as possible.

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