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This is an alternate guide for Impossible Ironman difficulty as the other guides were originally written prior to the release of XCOM: Enemy Within. It compliments the other guides and has spoilers, but no one should be playing Impossible/Ironman on their first playthrough. The first few months of the game are the most difficult, and it may take a few attempts to get through the first month in decent shape. After that it is manageable every time if played right. Even so, bad things will happen and damage must be kept to a minimum. Soldiers will die: make peace with it.

Starting Nation and Satellite CoverageEdit

XEU Satellite

Start in Asia for the Future Combat bonus, as it provides a great benefit throughout the game. Try to get South America and Africa covered early on (getting South America by May is usually when XCOM is ready to genetically modify soldiers so that works nicely). But don't let countries leave the Council just to get these earlier.

North AmericaEdit

Difficulty Base Funding Country Funding HQ Starting Money Maintenance Total
Easy §175 §270 §100 (-§80) §465
Normal §175 §180 §100 (-§80) §375
Classic §75 §180 §100 (-§55) §300
Impossible §50 §180 §100 (-§55) §275

South AmericaEdit

Difficulty Base Funding Country Funding HQ Starting Money Maintenance Total
Easy §175 §120 §100 (-§110) §285
Normal §175 §80 §100 (-§110) §245
Classic §75 §80 §100 (-§85) §170
Impossible §50 §80 §100 (-§85) §145


Difficulty Base Funding Country Funding HQ Starting Money Maintenance Total
Easy §175 §150 §100 (-§110) §315
Normal §175 §100 §100 (-§110) §265
Classic §75 §100 §100 (-§85) §190
Impossible §50 §100 §100 (-§85) §165


Difficulty Base Funding Country Funding HQ Starting Money Maintenance Total
Easy §227 §195 §100 (-§110) §412
Normal §227 §130 §100 (-§110) §347
Classic §97 §130 §100 (-§85) §242
Impossible §65 §130 §100 (-§85) §210

Base DesignEdit

Plan ahead for adjacency bonuses. Concentrate power facilities on the right-hand side. (Build power ahead of time, otherwise it will delay the next critical facility.) Steam is great but irrelevant if it's in the wrong place. Plan on building four Satellite Uplinks in the top two rows of the 2nd and 3rd tiles. Put your Cybernetics Lab in the 4th tile and build the Foundry directly below. Everything else fills in the gaps. It's more expensive to excavate as XCOM builds down, so don't go down unless needed. Build the Officer Training School as soon as possible (usually put it top left): the Squad Size I and II upgrades are important.

Research OrderEdit

XComEU XCOM Database Research Projects

Research Meld first, then build a Cybernetics Lab and create a MEC (just one suit). Soldiers are too easily killed to be worth gene modding for a while and require some autopsies anyway. MEC Troopers make quite a difference early on as their primary weapon, tactical subsystems and Collateral Damage are extremely helpful.

Alien Materials

To get Nano-fiber Vests.

Foundry: Tactical Rigging

Build a Foundry when it is affordable (for this, you need to research Experimental Warfare) and get Tactical Rigging to double the number of items a soldier can equip (expensive but worth it).

Carapace Armor

Body armor is next. It takes a considerable amount of time to research, but is needed. While Beam Weapons is also good it requires three research projects to get laser weaponry equipped on all classes of soldiers, a considerable investment compared to one project to equip an entire squad with armor. Also, Sectoids are usually easier to capture than Floaters, so XCOM may benefit more from the Beam Weapons research credit if laser weaponry is postponed compared to the basic armor credit if constructing armor is postponed. Also note that while Skeleton Suits are better, they may take too long for their benefits over Carapace Armor to be worthwhile.

Xeno-Biology and Arc Thrower

Research Xeno-Biology and the Arc Thrower. Hopefully by the time XCOM has an Alien Containment facility built, soldiers will have two item slots so some can equip a Nano-fiber Vest and an Arc Thrower (a Support class with the Sprinter ability is a good choice). Then try to capture a live Sectoid.

Weapon Fragments and Beam Weapons

This allows the construction of S.C.O.P.E.s and laser weaponry. Research Heavy Lasers before Precision Lasers and prioritize building Laser Cannons for interceptors, otherwise Abductors can't be shot down reliably.

UFO Power Source and Elerium

UFO Power Source research permits the construction of MEC-2 Sentinel suits, and unlocks the Elerium research project that is needed for Titan Armor.

Titan Armor

Not only is Titan Armor a life saver, but completing the project also allows the construction of MEC-3 Paladin suits.

Soldier Builds and Squad CompositionEdit

Main article: Squad Tactics (XCOM: Enemy Unknown)
XCOM-EU Soldiers

Play with the "Not Created Equally" and "Hidden Potential" Second Wave options enabled to increase soldier's individuality. Early on squads will consist of whoever is available, so learn to be adaptable. Two Heavy class soldiers can help considerably during the first few months. Rockets save lives: when an opportunity presents itself, use them – killing aliens with minimal risk allows a full squad to face the rest. Bring a Support class medic and MEC Trooper when they are available. A soldier that can break Overwatch is very useful: Lightning Reflexes is best, then Suppression. From May onward, XCOM needs to deal with robotic units, so including at least one HEAT Ammo Heavy or a Kinetic Strike Module MEC Trooper is also helpful.


The first Sniper should be a Squadsight, so that they have a fighting chance of survival. Squadsight was nerfed for XCOM: Enemy Within but is still good. Squadsights get Gunslinger, Disabling Shot (handy for capturing live aliens), Opportunist, and Double Tap. Later on, when soldiers have decent equipment (especially armor), Snap Shot Snipers can be invaluable with Damn Good Ground, Battle Scanner, Opportunist and In The Zone. Then ideally give them the Muscle Fiber Density and Mimetic Skin gene mods.


Give a well-attributed Assault all left-side abilities except Flush. Equip them with a rifle if the upcoming mission will be in open terrain (it is often hard to tell in advance) or a Council mission with Overwatching drop-ins. Equip them with a shotgun if it is a close quarters or particularly violent mission (e.g. early Terror Sites, XCOM Base Defense, Covert Data Recovery). Assaults with poor stats can be made all right-side (they'll still hit at close range with a shotgun). Do not underestimate right-side shotgun build: they are damage monsters. But they do tend to get killed.


XCOM's first Support should be a medic, i.e. all left-side abilities except maybe Rifle Suppression which is handy early on. The second should be a spare medic. Later on build a general Support soldier with lots of Smoke Grenade perks, Sentinel, and an Arc Thrower and/or Ghost Grenade.


Always choose Bullet Swarm, Shredder Rocket, HEAT Ammo (to help with the robotic enemies that begin to appear in June), Danger Zone, and then either Rocketeer or Mayhem. Consider Grenadier for a Heavy with an unusually poor Aim stat that can't shoot straight.

MEC TrooperEdit

XComEW MEC XCOM Database

Mechanize a Sniper early if possible. Their Platform Stability ability is good, and if XCOM already has a skilled Squadsight, a second may be redundant. A Heavy-based MEC Trooper's Body Shield is also good, but Heavies are valuable early on so consider mechanizing a Support instead if there are no Snipers available at the time. Build only one MEC suit (they require a lot of Meld), but mechanize a second MEC Trooper to wear it while the other is injured.

For the Tactical Subsystems, choose Kinetic Strike Module, Restorative Mist (always handy, especially when aliens use grenades), and Electro Pulse (a lifesaver against Sectopods). Keep in mind that XCOM must first research the Heavy Weapons Platform project at the Foundry to unlock MEC Close Combat and upgrade the Kinetic Strike Module with +50% damage.

Choose Advanced Fire Control and Damage Control for an early MEC (when 2 HP really helps) or Vital-Point Targeting for a late-game one. Jetboot Module is always useful, along with Expanded Storage for increased ammo and Restorative Mist. As for Absorption Fields: being hit for more than a third of a MEC Trooper's health is more common at Impossible difficulty than at the lower difficulty settings.

Covert OperativeEdit

An Operative should be a soldier that isn't invaluable to be in the squad, and who is in need of promotion. It's a good way to get Squaddie Snipers that crucial first promotion (Operatives get extra experience points). Equip them with a Nano-fiber Vest, and ideally a Respirator Implant for an additional boost to HP. On a Covert Extraction mission, keep them hidden near their starting point until the squad finds and kills at least two packs of EXALT troops before approaching the comm arrays, and try to have the operative finish off the drop-ins. On a Data Recovery mission it can be difficult to get kills, so just try to keep them alive.

An Operative with Mimetic Skin can run around with ease on a Covert Extraction mission, or hide in the encoder zone to prevent EXALT from decoding during a Covert Data Recovery mission. But since the February 2014 patch made Mimetic Skin more expensive, this may not always be feasible.


Test soldiers at Colonel or Rookie/Squaddie rank, never in between. Choose Psi Inspiration: It may be rarely used, other than before busting a UFO bridge or when a Sectoid Commander is on the loose somewhere, but it's still better than Psi Panic. High-Will Psionics (over 100) should have Mind Control, while the weaker ones can use Telekinetic Field. Ideally squads should consist primarily of soldiers capable of Mind Control; it is great in nasty situations as the aliens will often focus their fire on a mind-controlled peer, which means one less alien to deal with, and less fire directed towards the squad. If it survives, it can be used to take suicidal flanking shots or toss a grenade. Ultimately, not all squad members need to be Psionic, it's not as critical as the fluff implies.

Gene ModsEdit

XComEW Genetic Modification XCOM Database

Save Meld for important strategic mods rather than using it for several small improvements. Apply them after researching decent body armor, so that the recipient has a better chance of surviving.

Use Muscle Fiber Density for a Snap Shot Sniper. Secondary Heart is beneficial for key soldiers such as Psionics or Snap Shot Snipers. As for brain mods, Neural Feedback is better (and cheaper), although Neural Damping is safer for Heavies and Snipers, who can butcher their buddies if allowed (a mind-controlled In The Zone/Opportunist Sniper is very bad indeed).

Potential candidates for Mimetic Skin include: a Support medic used as a scout (especially if Psionic), a right-side Assault (not a left-side one, as it creates problems with Close Combat Specialist and Lightning Reflexes), or a Snap Shot Sniper (works in half cover). Consider waiting until the late-game for Mimetic Skin, as it is expensive to risk on a soldier that is easily killed or has sub-par Will. But it could be worth the risk: it is very helpful for scouting and obtaining Meld.


In March grenades are great, as are Medikits, so carry both. In April consider using Nano-fiber Vests. Once soldiers can carry two items, equip Snipers and Heavies with S.C.O.P.E.s. Reaper Rounds are also good for Snipers and Assaults, and Respirator Implants are useful for Squadsight Snipers. Chitin Plating should replace Nano-fiber Vests as soon as the necessary Chryssalid corpses are available (consider equipping all soldiers with a HP-boosting item for Impossible Ironman). Combat Stims can be useful on a right-side Assault as they don't otherwise have critical hit immunity: when stealthed and aliens are spotted, use the Stim, shoot a couple, and then take the punishment. The usefulness of Mimic Beacon seems to limited compared to other the items.

Flashbang, Needle, and Gas Grenades have their uses, but do not compare to Ghost Grenades. They can be used in two ways: First, as a life-saver; if a soldier reveals an alien pod and is flanked/exposed, ghost them. Second, for coordinated stealth attacks; if there are aliens through a door (e.g. a UFO bridge, or last room of the Temple Ship Assault), use Ghost Grenades to stealth squad members, run in and take position, then fire from close range / flanking positions.


XComEW Medals XCOM Database

Urban Combat Badge: Choose the cover bonus and give it to any non-MEC Trooper soldier.

Defender's Medal: Choose the extra Medikit HP (the other benefit seems negligible for high-Will soldiers) and give it to MEC Troopers or Assaults.

International Service Cross: Choose the Aim bonus and give it to anyone except a Support (better Aim bonus for the biggest guns).

Council Medal of Honor: The +10 Aim/Critical Chance if 7 tiles away is good for Squadsight Snipers, MEC Troopers and Assaults.

Star of Terra: Choose the Will/Defense bonus and be sure to give it to soldier that is often taken along on missions, ideally a Psionic.

Early-Game CombatEdit

Mid and late-game is mainly about using abilities properly. Do think about firing order. Don't go rushing forward if most of the squad has already used its actions. Most aliens should die before they get a turn.

Early-game combat is different. It's riskier and harder. The number of soldiers is limited, and they are easily killed. They also don't have a lot of abilities and their Aim is poor. Engagements will last more than one turn.


Don't get into firefights if they are in full cover, even if when the soldier is too. A Sectoid's Aim is similar and their Crit Chance is higher if boosted by Mind Merge. Kill the transmitter for a double-kill whenever possible; it can be worth pushing forward a little to spot it for a Squadsight Sniper, but don't overextend. Fall back when necessary, allowing for an Overwatch shot and sometimes causing them to dash into sub-optimal positions where they can be flanked the next turn. Consider having soldiers duck completely behind full cover so they can't be seen (provided they are not close enough to flank), then emerge on the other side the next turn (still in full cover) to see if an enemy is nearby and perhaps get a flank. Use a solider in (preferably indestructible) full cover to Hunker Down and draw alien fire while other soldiers move to flanking positions out of sight. Bullet Swarm Heavies can shoot then Hunker Down to win long firefights. Be wary of rushing forward, e.g. with Run & Gun.

Later in the game, triggering multiple packs is manageable but in March it's a nightmare: squads only have four soldiers and most don't have double-shot abilities. MEC Troopers are not as tough as them may seem. Don't leave them where they are going to get shot at: if necessary leave them hidden away behind full cover so they can leap out and use the Kinetic Strike Module or Flamethrower the following turn.

Thin MenEdit

Thin men are the hardest aliens relative to when they appear. Don't engage in equal firefights. Don't position soldiers too close together or a Thin Man will use Poison Spit. There's not much point Hunkering Down or using Suppression: they'll retaliate with poison. Ideally don't let Thin Men start their turn able to see a soldier. Have a Heavy use a Rocket if possible. Otherwise consider the fall back and Overwatch tactic. But remember Thin Men can move fast and Leap: don't get flanked. If in a firefight, prioritize any targets in an elevated position as they are the biggest threat.


XEU Muton

In May they only carry Light Plasma Rifles (except on Slingshot missions), so they are tougher but not much more dangerous than other early-game aliens: they have better Aim than Thin Men but are less mobile. They are good candidates for Shredder Rockets: a regular rocket won't kill them and is best used on Thin Men or Floaters that can be taken out quickly. Mutons have a nice habit of using cars for cover.


Floaters don't tend to hide or be very tactical, unlike Thin Men. If one uses Launch to get behind the squad, they have a full turn to kill it. Floaters often bunch together nicely for a rocket.


Keep soldiers together and go on Overwatch: a Seeker will attack one, and everyone else gets a shot on it. First important point: if a Squadsight Sniper doesn't have strangle immunity (provided by a Respirator Implant, or Titan/Archangel/Ghost armor) and a Seeker appears, have the Sniper dash to join the rest of the squad and/or have a MEC Trooper/Assault run back to them. Second important point: in April don't give the whole team strangle immunity: if a Seeker can't find anyone to strangle it will shoot its plasma weapon instead, which is worse.

Early-Game MissionsEdit

First Council MissionEdit

XCOM-EU The Council
Bomb Disposal

If the first Council mission is a Bomb Disposal, it may prove to be very difficult and be best to skip it.

Target Escort

The first Target Escort mission is typically Dr. Hongou Marazuki, which takes place at an observatory. Stay put at the beginning and use Overwatch for the first two Thin Men that drop-in. Then work your way outside around the right hand side of the building. Don't worry about cover, another Thin Man will drop by the truck but it should be easy to kill and there are no other aliens nearby. Then head up to the roof and plant any Snipers/Heavies behind the half cover air conditioning units. There is a Thin Man on the other side of the building. Trigger it carefully and kill it that turn, using grenades if necessary.

There are three groups of Sectoids amongst the tanks. Send a soldier forward towards the alien device near the truck to trigger one pod, then fall back. This should draw the Sectoids near, to be taken out by the Overwatched soldiers on the roof. Use the same method to for the next Sectoid pod. The third pod is over by the far corner. Position soldiers atop the the other observatory building and do the same thing. Be cautious of the last last Thin Man, who drops-in onto the roof.

Target Extraction

The first Target Extraction mission is typically General Peter Van Doorn, which takes place on the collapsed highway map. Proceed carefully, as there is a Thin Man on the right-hand side. There are Sectoids on the left, in the pit. Do not go down, instead creep forward to the edge, triggering the pod on the other side. Don't get into a firefight with them. Instead, have a Heavy fire a rocket if the Sectoids are bunched together and/or have a MEC use Collateral Damage if they are near a car. Otherwise, fall back a little to the half cover not far behind. The Sectoids will come forward into the pit, and Overwatch can be used to shoot at them with a height advantage. Only when they are all dead (the alien turn becomes instantaneous) is it safe to proceed down into the pit and rescue Van Doorn. When this happens, Thin Men drop into the pit and on the left-hand side. Move Van Doorn very slowly, and only trigger one Thin Man at a time. The last two Thin Men drop-in back towards the Skyranger. If a rocket is available, use it.

First Terror Site MissionEdit

Chryssalids are quite tough, and require substantial firepower. A MEC Trooper with a Kinetic Strike Module is very helpful; although they may run out of ammo quickly, they can one-hit a Chryssalid. The most important thing is not to have anyone killed by a Chryssalid: not only is the soldier gone, but the remaining squad members must abandon their positions and fall back. Otherwise, the resulting Zombie will be problematic and can quickly lead to the death of a second soldier and eventually the loss of the entire squad. Keep soldiers an adequate distance away, with clear lines of sight to help prevent enemies from creeping up from behind. The Floaters should be taken out with a Heavy's rocket or otherwise dealt with as efficiently as possible: it's difficult to deal with a combination of ranged and melee enemies at the same time.

If the mission takes place at the police station, be extremely cautious when going inside: it can be a death trap. If the mission takes place at the large warehouse on the docks, go inside: it's the best place to see everything coming. If it takes place on the highway, proceed slowly and let the aliens approach the squad: the upper area is a nasty place to be. Try to make sure some civilians survive (if they all die the mission is a failure), but don't worry about saving them all and never engage in risky behavior to save one.

Slingshot MissionsEdit

XCOM-EU Missions - GangPlank

Operation Slingshot missions are difficult but worth it. Note that the Battleship in Gangplank consists mainly of Thin Men and Chryssalids, not the tougher enemies that are typically encountered on Battleships later in the game.

Progeny MissionsEdit

The Operation Progeny missions begin with what may be the toughest of the three. Portent can be problematic due to the number of drop-in aliens that are scattered over a large area, making it difficult for the squad to eliminate them all in the turn they arrive. It may be advisable to skip it unless a particularly good squad is available by that point. The ensuing missions are relatively easy in comparison.

Alien AbductionsEdit

Choose abduction missions primarily to minimize panic, taking into consideration the other Council nations on that continent. Failing to respond to an abduction increases panic by three in the target country and one for the rest of the continent. Basing a decision on the potential rewards is tempting (especially a a country that offers Engineers the first month), but always consider what the strategic cost is. All things being equal, for the first abduction it may be advisable to go for one that's "difficult" as opposed to "very difficult," as there are fewer enemies (10 instead of 12).

Alien Base AssaultEdit

Go for the alien base as soon as possible. Note the aliens species get tougher as months go by, it may be easier at the end of May even with mediocre body armor and conventional weapons.

After the Alien Base Assault, make sure the top six soldiers on XCOM's roster are equipped with the best gear available until the XCOM Base Defense occurs (re-equip them after each mission if necessary). It may be possible to modify which soldiers are at the top of the roster during that time: send desirable soldiers on missions to increase their standing, and send undesirable soldiers to either the Psionic Labs for testing or to the Genetics Lab for modification.

General TipsEdit

  • Remember that XCOM needs Phoenix Cannons to reliably shoot down the Overseer ship, and Laser Cannons to shoot down anything larger. So prioritize their research and construction as needed. Alien ships have lots of important resources on board so it's a shame to miss any opportunity to acquire them.
  • Use the roofs - but keep in mind that they usually only offer half cover so don't remain there too long in a sustained firefight. Sometimes it's good to travel along the middle of a roof to avoid revealing alien pods. When a soldier on the ground finds some aliens, send the soldiers on the roof to the edge and get a flanked shot from an elevated position. If the aliens are inside a building, have them drop down and get a point-blank flank shot.
  • Don't forget Collateral Damage from the MEC: it's a great way to detonate cars for 6 damage (more for truck cabs and tanks) and also to remove cover.
  • Meld: do go for it but don't overextend. Getting one canister per mission is decent. It's not worth risking veterans for. The suicide Rookie strategy may be ill-advised, as it may not be worth having revealed enemies roaming the map to ambush the squad.

See AlsoEdit

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