This is a guide for those who want to win Mars Horizon under the most difficult conditions: very hard difficulty, ironcore (so no save-scumming or reloading), and using auto-resolve for all missions (which I have found makes failure much more likely).

It draws many ideas from tcelvis’s “Gaming the System” (https://steamcommunity.com/sharedfiles/filedetails/?id=2303265446) – []  but the approach and reasoning is somewhat different, as are the points I think are most important to focus on.

Introduction and Goals

The goal of this guide is simple: to give some advice and help about winning Mars Horizon on what I have found to be the hardest settings: very hard (obviously), with ironcore so you can’t give in to the temptation to reload, and auto-resolving all missions (yes, literally all of them) because I find that the chance of failure is higher with auto-resolve than when you do the missions on your own–which is as it should be, of course.

Note that this technically requires less skill at gameplay because we’re stripping out the mission resolution minigame: it’s harder because it’s more likely to fail, not because it’s actually more difficult moment by moment.

But if, like me, you’re looking to conquer Mars first despite the increased risk of failure, or even because of it, read on!

Choosing and Customizing an Agency

So the difficulty customization is basically set for you by the difficulty I’m addressing: very hard/ironcore/auto-resolve all. I disable the tutorial; you don’t have to, I suppose. But that brings us to the real decision:

Choosing and then customizing your agency.

Since I highly recommend customizing the agency bonuses, it doesn’t matter as much which agency you choose. But there are three things to remember when you’re choosing an agency even when you don’t keep their bonuses the same: you get their tech tree, you get their base layout, and crucially you don’t have to play against them.

For these reasons, I recommend China (I use China) or USSR/Russia (they usually win if I don’t, so getting them out of the game is valuable). China’s tech tree is simply great: not only do they have a lighter Crewed Moon Landing load than anyone else by a large margin, but their early-game rockets are great. A Long March 1/Long March 1 can make it to Lunar Orbit, and a Long March 1/Scout can put an Animal in Space. A Long March 2 (with the appropriate supplemental booster of 4 more Long March 2s) can even lift a Crewed Moon Landing.

Compare this to NASA, for instance, which needs a second-tier booster to reach Lunar Orbit.

So I recommend China.

Then you get to customize the bonuses.

I recommend Pathfinders first and foremost: you need that reduced Mission research cost to get anywhere with the disadvantages we’re piling on voluntarily, and honestly the late-game techs are so expensive you’ll wish you had it if you don’t.

To fully fill out your bonuses after taking the 2-point Pathfinders, you’ll want one negative (malus): I recommend Not Because It Is Easy, since we’ll be running behind most of the game anyway and skipping a lot of milestones, so we won’t even get the top-three bonus anyway. This is one place where ironcore limits our options: no reloading means Failure Is Not An Option can be a real problem, as can the lowered payload or launch reliability options.

There’s a little more flexibility in your other three points of bonus than you might think, but I recommend the three Economical bonuses (Architecture, Assembly, Construction). Money is tight, especially midgame, so these help a lot. tcelvis’s guide – [steamcommunity.com] to very hard recommends Operations Specialist, and I can see that being useful, but I find that a) early game I don’t have enough missions to fill the extra slot before I’d get a Mission Control anyway, b) midgame I can barely afford the missions for the slots I have, and c) late game I don’t need it. But that ‘s my style, and choosing it does mean you could theoretically research and build one less Mission Control expansion. Expansion Expertise could be useful (building research is hard to discount otherwise), as could In the Name of Progress (avoiding penalties for failure is great in ironcore), Rocket Scientists (you have to reach the end of the Vehicles research tree, after all), or even Bidding War (China’s contractors aren’t the best). Just be aware of what you’ve chosen and play towards it.

Then make sure to randomize your opponents so you have an Ally (Japan is the best option for their contractors, but I did win with ESA: the key is to have someone who gives you a science bonus, additional contractor options, and cheap Joint Missions) and at least a Competing, ideally an Antagonistic agency (for funds boosts).

Once you have your chosen friend and enemy, you’re ready to actually start the game!

The Early Game (Era 0-1)

The early game is fairly straightforward, since there are fewer choices. Get your Test Launch up as early as you can and keep pumping out the Test Launch request missions. Since there’s no penalty for failing them, I personally don’t really care what window I’m launching in, and since you don’t get a new Test Launch request mission until the most recent one clears out, I try to pack in as many as possible. If you want to space them out once you have the Research Lab up and get some Science Training in, that’s up to you.

Research Small Launchpad first, so you can launch your first launch and (probably) get the first Milestone bonus. You don’t want to launch Artificial Satellite because those request missions are not as good, so you actually can go building-heavy in research at the start and still win or almost win the race to the second-level milestones (Lunar Orbit or Animal in Space). I suggest Small Launchpad, Research Lab, Spacecraft Assembly Facility, Backup Power Generator. Build the Launchpad, Lab, and Generator; don’t build the Facility until later (when you can place it to get some nice little bonuses to your outputs by adjacency). Why this order? You need to launch rockets (Launchpad). You want both bonus science and the use of Science Training which you’ll use most of the time (Lab). And you want both cheaper payloads and to avoid the power cut event (Generator). The Facility is needed for what it unlocks: both the Generator and later on the Mission Control. But you don’t have the money to build or maintain it early game, so you can ignore it.

Place your buildings for maximum adjacency bonuses, noting that some of them give negatives if placed adjacent. Avoid that.

After the building rush, I suggest rushing missions: Artificial Satellite and its payload first, and then the second-tier missions.

Since we’re not launching Artificial Satellite, you’re guaranteed to get the event that asks if you want to praise or dismiss the achievement of the first satellite in space. This is an easy decision, in my eyes: if it’s your ally, praise (as dismissing will make them not your ally anymore); if not, dismiss, as it comes with a healthy support boost especially for early game.

Here’s the first major decision point: do you go for Animal in Space, which is slightly more expensive and generates fewer missions, but gives bigger rewards immediately, or do you skip it entirely and go Lunar Orbit? Either way can work. I recommend going for it, though: if you don’t, you can’t really go back, because you get the event around humanitarian outcry over animal missions, which either means you can’t do them or gives you a support cut for choosing to do them. I’m still not sure if that triggers from order (being 3rd or later to do Animal in Space) or from time (how many months have passed) but either way, delaying Animal in Space means losing those missions. You can always get Lunar Orbit later (and you should: those are important request missions early game).

So I recommend Animal in Space and its payload, followed by (finally) your boosters and upper stages: assuming you chose China, that’s Long March 1 and Long March 1, then Scout. Why Scout? Because it’s the cheapest to research of the upper stages that can carry Animal in Space, as well as the cheapest to build.

Keep running Test Launches until you’ll be able to get Animal in Space up, both the payload built and the rocket built by the time the payload is done.

Then launch Animal in Space. You should be early enough relative to the AI to continue getting the missions; keep doing them. Use the science you gain to get Mission Control, and then start doing 2 missions at a time. Get Lunar Orbit and its payload: Animal in Space only gives you 3-4 missions (high value, but then exhausted) whereas Lunar Orbit will continue generating requests for the rest of the game.

You’ll probably get the event that asks if you want to praise or dismiss the Lunar Orbit as well: if so, the same rules hold that you want to keep your ally friendly but you want the support of dismissing anyone else. Besides, if you can annoy a second agency into Competing or Antagonistic status, you’ll get an additional funds boost that doesn’t hurt.

Then get the Research Lab expansion (you want those 50 science a turn, plus you’ll need to get to the Robotics and Aeronautics labs eventually).

After that, move on to Satellite Imaging in the following way (this is important because Satellite Imaging generates a timed quest to launch it, which triggers when you research the tech, so you want to prepare properly): get one more booster and one more upper stage to unlock the level 3 vehicles (I suggest Algol/Able, but you do you). Then get Medium Launchpad, since you’ll need to build it. Then get Satellite Imaging (accept the quest) and its payload. Then while you’re building the payload, research Tsyklon and Long March 2 (upper stage). Those will be your rocket to launch the Satellite Imaging. Star-37 is cheaper than Long March 2, but needs a more expensive booster that also takes longer to build; you’ll pick it up to unlock the next level of vehicles but don’t try to use it here. Similarly Long March 2 (booster) is a good booster you’ll want going forward, but it’s more expensive and takes longer than Tsyklon, so avoid it for this mission.

Once you’ve launched your Satellite, you should get the other 2 vehicles (Star-37/Long March 2 are my preferences, but Deltas are fine) and then unlock Contractors. Especially if you have Japan as an ally, you want contractors; even if you don’t, you’ll need to get past it to get the other boosters and uppers, so you don’t want to forget and end up with a Venus mission you can’t send out until you unlock it, wasting a mission slot.

If you’ve done this, you’re through Era 1–and probably well behind the AI. That’s OK. The AI will spread out across the whole tech tree and start doing really long outer planet missions later in the game, and you’ll catch up. Don’t panic. This is a long haul to Mars, and you’re well on your way now.

Midgame 1: To the Moon (or Not)

The second major decision you need to make is this: are you going to launch a Crewed Moon Landing or not?

If you aren’t playing as China, this is actually not much of a choice. A Crewed Moon Landing requires a Large Launchpad and a big, expensive rocket (not to mention an Astronaut Training Facility, which you’ll noticed we haven’t researched yet). So you’ll skip it, and go down the part of the tech tree with Commercial Satellite/Commsat instead.

If you are playing as China, you can get away with a medium rocket (you already have a medium launchpad) and so it’s a real decision. I’ve been the first to launch a Crewed Mars Landing either way, so it’s clearly all right to go either route. Here are some factors that might influence your choice:

1. Will you torch your support? If you took the bonus of avoiding penalties for mission failure, or if you’ve found the Onboard Cameras that allow you to avoid the penalty for a specific mission, you’re fine even if your astronauts die. If you didn’t and haven’t, you’re going to lose 1125 support every time you fail a moon landing, and that’s a lot to risk in ironcore/auto-resolve (note that this includes both exploded rockets and failed missions).

2. How’s Venus looking? Whether or not you go to the moon, a lot of your science in this part of the game is going to come from Venus missions: first the Impacter and then its request missions, and then the Orbit and its request missions (more on this below). Like all your missions with auto-resolve, these get easier to do the more you do them successfully (there’s literally a boost to auto-resolve based on ‘similar’ missions completed). So if Venus is going well, maybe you don’t need the moon; but if you’re failing Venus missions, maybe you want to shift gears a little bit and go lunar. After all, lunar missions are single-month events, and don’t have a long period of bad launch windows associated with them.

3. Do you want or need the support? Opposite to #1, if you feel you’re behind on where you want to be on support tiers, and so on income, you might need to go to the moon precisely because while it is high risk, it is also high reward. Nothing (except the very late Mars/big telescope missions) comes remotely close to the moon in terms of support bonuses, and when you factor in how early it comes and how cheap it is, it can be a huge boost if all goes well.

So once you’ve made that decision, you’ll orient either towards going to the moon or going Commsat. I don’t think you need both: they’re separate research lines, and you’re already behind. Plus, Commsat gives money-only missions, which you need less of if your support is boosted by the moon landings–and you’ll still get some lucrative-type missions along the way from the other types even if you don’t have Commsat.

Either way, you want to start by researching Venus Impacter and its payload. Then you’ll want the Centaur-C(the cheapest upper in terms of both money and research that will make it to Venus). Then you can start spamming missions: Lunar Orbits, Satellite Imaging, and Venus Impacters. You should have enough missions to fill up your slots without having so many you don’t have the cash for them: grab lucrative missions when you can. Note that the Venus missions are the only ones at this point where you’ll get upgrades as a reward: prioritize the Composites that give you a money discount, the Onboard Cameras that ignore failure penalties (especially if going to the moon) and eventually the shock absorbers that give a payload boost.

Use the science you generate to research Mission Control Expansion, and then down the Research Lab side of the tree: the second Lab Expansion, and then the Robotics Research Lab and Aeronautics Research Lab–in that order, since you need to research missions before you need their vehicles. Once you have the Robotics Lab up and the Aeronautics Lab researched, go ahead and hit Venus Orbit and its payload. Then get the Bloc-D upper so you can do that mission and run through the manned-orbit techs that you’ll need to research to unlock the next level but don’t plan on using: Multicrew Orbit and its payload and then Orbital EVA.

At some point either when you get a bonus to vehicles research or once the Aeronautics Lab is up, start running through the vehicles too: this is more important if you’re going to the moon than if you’re going Commsat, but you will need to eventually do it anyway to get to Mars. For the moon, get at least to Long March 2F and the 4x Long March 2 supplementary boosters. If you happen to get there, Titan IIIis a cheaper booster option as well. For Commsat, you actually just need the easier-to-get R7 Soyuz upper and you can use existing boosters. My recommended tech list for this (based on research cost/utility/use cost) is 2x SRB/R7 Soyuz upper/Bloc-D upper/Centaur-C upper (you should already have the last two for your missions). Then Long March 2F/4x Long March 2/N1. Why the N1 even though other options are cheaper to research? Because you’ll need the N1 at the end of the game to avoid researching more expensive boosters for your Mars mission, and you might as well get it here to unlock the next tier of vehicles anyway.

Once you can, unlock your chosen next tier of missions: Commercial Satellite or Crewed Moon Landing and the respective payload, and send them up! If you’re doing Crewed Moon Landing, don’t forget to use the time while it’s building to research and build the Astronaut Training Facility or you will be disappointed! If you’re not, go ahead and get moving on vehicles or missions (I recommend vehicles) while they build. They (especially Crewed Moon Landing) take a while to go up, so you should focus on moving into the next part of the midgame: everything but Mars.

Midgame 2: Going Everywhere But Mars

The longest slog of the midgame is the part before you get to go to Mars but after you’ve made the Commsat/Moon choice. It’s a lot of similar missions over and over, and building up both money and tech so you can safely make a run at Mars, stealing it out from under those better-prepared, more expansive agencies run by the AI.

But even though I just said it was a slog, it can actually be one of the most fun parts of the game, because it’s somewhat free: a lot of the tech you’re researching you won’t use immediately, so you don’t really have to stick to any particular order of techs, and a lot (basically all) of the missions are going to be request (or at a pinch, joint–request are generally better because the rewards are better, and while you share the costs with a joint mission, you still have to spend all the time for it) so there’s more flexibility there too, and every game is different.

What you want to have done by the end of this is to have everything but the Mars prep missions researched on the mission tree, be down at the last levels of the vehicle tree, and at some point grab the Vehicle Assembly Building and the Large Launchpad–and build at least the pad (though I do find the lowered time to build of the VAB useful, it’s not required and is expensive). If you haven’t gone to the moon, you’ll want to pick up the Astronaut Training Facility too, though you can actually grab this all the way at the end if you need (I’ve done it–it’s kind of hilarious to research that while the Crewed Mars Landing is being built).

When I say “everything but the Mars prep,” though, there’s a big caveat: we’re skipping one whole section of the tree. We are not building or researching or even thinking about Space Stations and their ilk, because that’s a whole investment in research we do not want to have to do. Why skip that and not anything else? Two reasons. One is the reason tcelvis gives in their guide – [steamcommunity.com] : they just aren’t that efficient. But the other is that this is the only part of the mission tree you can skip at this point, and the less research you have to do, the better. We’re also skipping researching any Saturn missions (the Jupiter missions are always cheaper to research and we’re not going to fly them anyway because they take too long for too little reward). But the whole space station side of the tree is independent in a way that the other side is not, so we’ll skip it.

Why is this? It’s because to do Mars requirements we need to have done 3 of the 4 Mars preps. And the space station line leads to the Ground Hab–you could get all the way there without researching any other line of techs. But the path to any of the other 3 intertwines at the point where the Mars Lander & payload and the Jupiter (or Saturn, but see above) Flyby & payload intersect as requirements to both the Neptune/Uranus Flyby pair and the X-Ray Telescope. Since you can’t avoid that point if you want 3 Mars preps, you might as well focus on that side entirely, and not bother with the Space Stations at all.

So that means we’re researching the following: Jupiter Flyby and payload; Mars Lander and payload; Neptune and Uranus Flyby; X-Ray Telescope and payload; Grand Tour; Jupiter Orbiter and Payload; and Space Telescope and payload. The only ones we want to actually fly are the telescopes, and maybe the Grand Tour (with auto-resolve, I think this isn’t worth it because it has so many stages, but it does have a good payout and you can usually do it first, so feel free to try. I usually try once and then drop it when it fails, since the AI rarely fails it).

To do this, we’ll need a little vehicle research too (and of course we’ll need them for Mars). The Long March 3 can carry up to the X-Ray Telescope (“Insight”) payload, and it needs only the already-researched Long March 2 + 4x Long March 2 (or the Titan III or Delta IV) to launch. For the heavier Space Telescope (“Xuntian”) payload, we’ll need a bigger upper: the first available is the Wyvern (upper, not booster), or the shuttle (“Divine Dragon”) if you have a Large Launchpad already (if you don’t, stick your Wyvern on a boosted Delta IV). This means that I recommend the Wyvern, 2x Delta IV, and one of the other two supplemental boosters for this level of tech–the Divine Dragon is more expensive, but if you play with a LOT of telescopes, it’s also worth it for the cheap cost of revamping it each time. If you don’t, skip the cost for research.

(The Wyvern will also let you get two of the three required Mars prep missions off the ground, but not the third).

As you make the turn towards Mars, you will want to have at least two and probably more telescopes up: they take a long time to get their full tech payoff (20 years) but honestly from first launch of an X-Ray Telescope to the point where you’ve researched and successfully sent off your Mars mission is usually in that range–and even if you only recoup 3/4 of the science, it’s still worth it.

By the time you head to Mars, you will need the Large Launchpad–so I try to end this segment of the game with it researched and built, because it also makes some of the earlier missions easier if you use a larger rocket. And you’ll need that Wyvern and something to carry it (Delta IVs or one of the large boosters) both for the last telescope and for those first Mars missions.

Next stop: Mars itself!

Endgame: Mars Itself

The irony of this approach is that by focusing on the moon (whether Crewed or not), Earth, and Venus, we haven’t actually sent anything to Mars yet.

This will have to change to win the game.

You’ll need 3 Mars Prep missions, 2 Mars Requirement missions, and the actual Crewed Mars Landing. That’s a lot of research on its own; add to that the need to get to the far end of the vehicle tree, because literally only the last upper stage (for China, the Long March 9) is allowed to carry the Crewed Mars Landing payload, and you can see that this “endgame” can be quite long. Fortunately, that lets your telescopes help you more and more, so it’s not all bad. Also, the AI sometimes gets quite bogged down as well, giving you a chance to catch up.

I usually start this phase by researching one of the two Mars rovers in the center of the tech tree: Mars Prep: Mars Exploration with the Perseverance rover or Mars Prep: Robotic Rover with the Tianwen-1 rover. Since I only have 3 mission slots, I keep one on Mars while the other 2 provide cash (via lucrative missions) or science (via…everything else, usually Venus or Earth Satellite, with the occasional big telescope) to make sure I don’t stall out on the research. Sitting there with only ~200 science a month can take a LONG time to get all that research done, so make sure you’re not falling behind on making science-producing missions happen while you go to Mars.

While I’m prepping and sending that mission (and they take a long time to build and then to find a good launch window), I go down the vehicles tree. The goal is twofold: first, the Long March 9B for the last Mars Prep (Crewed Rover) and the Mars Requirement: Crewed Lander, and then the Long March 9for the Crewed Mars Landing. The Mars Requirement: Engine and Habitat takes a big upper stage too, but it can be the Long March 9 or the Long March 9A, depending on what you research to unlock the Long March 9.

Basically, I go down the vehicles tree as far as I can with the one of the center Mars Prep missions, then use the science from that mission to get the other central mission, then while it’s going out I research more vehicles, and then I do the last Mars Prep (Crewed Rover), and use the science from it to get the Mars Requirement: Crewed Lander going. Then while the Mars Requirement: Crewed Lander is going, I’m pushing further to get to those big last vehicles. Ignore the other two vehicles on the bottom row: you’re using the N1 to go to Mars (along the way, try to find a couple chances to test it out on other missions, so it gets promoted to a reasonable launch chance). The only thing you definitely need is that Long March 9.

I usually use the 9A for the Mars Requirement: Engine and Habitat, but if you’ve already got the 9 researched, then use it so that it also gets a higher level for your final Mars mission.

Remember, you don’t need the Mars Crewed Landing and the Huoxing-1 until everything else is done: you literally can’t launch it if the Requirements aren’t complete. Research it last.

Well, almost last. If you didn’t go to the Moon, now is the time to get that Astronaut Training Facility while you wait for the Huoxing-1 to build and to have its vehicle (N1/Long March 9) built. If you finish that, or if you already did it for the Moon, I recommend going back to the very first techs and filling out your tree so that you get the bonuses like Space Systems Experience (increased payload %) and Launch Systems Expertise (increased launch %). They’re quick and the bonuses help. This is also a good time to make sure you build that Spacecraft Assembly Facility: training Science on the last mission won’t help you (or even missions–failure is worse than low science output here).

Eventually, you should reach the point where you can actually launch that final mission, with the others nipping at your heels.

You shouldn’t be hurting for cash here, between lucrative missions and support increases that fuel budget increases, but if you are, remember: a tie is better than a loss, and you should still have an ally, so you can do a joint mission with them. It’ll save you cash for that last mission, and as long as you don’t lose that mission you’ll be fine. I recommend it especially if you DO lose the Mars Mission on your own, and need to rebuild a second time before someone else wins.

The last mission will be agonizing. You haven’t done all 4 Mars preps, and you didn’t take the time to build up a bunch of extra missions for experience, plus if you did it my way you only have Level 1 Astronaut skills, so you will be at ~25-30% failure chance for each stage of the mission (excluding launch). This is why I recommend training Payload for this mission, as it helps a little.

You may lose the mission. Fortunately, this gives a 50% speed boost to rebuilding the vehicle, and the combination of weird launch windows to Mars and the AI always (fortunately!) putting its launches over a year after the vehicle is done may give you a window to slip in with a second–or in my experience, once even a third–mission.

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