Rapid Early Expansion (REX) – Stellaris Tactics

June 6, 2022 by Solar Cross

Rapid Early Expansion, REX for short, is the strategy of the land grab. Be there first and defend it from a position of strength. It is the polar opposite of the early conquest strategy, where you let your rivals invest in expansion while you invest in the means to take their investment from them…

This article will show the perfected REX strategy for Stellaris. First we must ask who should REX and why.

Rapid Early Expansion

Just as the early conquest strategy suits the militarists, the subjugators and the xenocidal, so the early expansion strategy suits the pacifists and the economists. It is the mandatory early strategy for Inward Perfectionists.

The Inward Perfectionist (civic) can neither do aggressive militarism, nor cover for pacifism through alliance building. If the peaceful autists are to have anything they must claim it before anyone else and then stand alone on it against all comers.

On Not Chasing Too Many Rabbits

He who chases two rabbits, catches neither.

– Confucius

An optimal REX has quite specific inputs. These inputs, or resources, could otherwise be deployed for a tech rush or a colony rush or a fleet rush. The first thing to get straight is that by REXing you not doing these other things, at least until you are done REXing. Otherwise you will be doing the everything rush, which is no rush at all.

In particular you start with all the technology you need to REX so any investment in tech in the early game is ultimately to the detriment of a REX. Those resources invested in tech could otherwise be invested in alloys and unity and so on.

Once your REX is done, you can catch up on tech.

Ingredients of a Rapid Early Expansion

Ultimately a Rapid Early Expansion is the spamming of outposts to claim systems. Also, there is some cunning in the exact order that outposts are built, and where, in order to corral the maximum number of stars for the least amount of time and resources. See the Star Corralling tactic later.

In the end though, we are looking to maximise outposts until we bump up against rival empires and our borders begin to settle.

The ingredients of an outpost are influence and alloys. They are built by construction ships of course. Generally one construction ship is enough for most early games but for a REX at least one more is better.

Before we can build an outpost in a system we need to have it surveyed by a science ship. Surveying is quite a slow process, so it is a potential bottleneck. Multiple science ships are important then. Science ships cost alloys and need to be piloted by leaders who cost unity.

There are number of traditions that have significant benefit for a REX and they also cost unity.

So to fuel a REX we need alloys, influence and unity. Our early economy should be focused on producing these. It helps to have a decent surplus of minerals too to help with building mining and research stations.

Minerals will also be wanted for reworking the buildings and districts on our starting planet to optimise for REX.

Now that we know what our REX ingredients are it is time to consider how to deploy them for maximum effect.

Star Corraling – Tactics for System Enclosure

It takes time and resources to survey and claim a system. However with some smart prioritising we can corral for ourselves systems we have neither surveyed nor claimed. Once outer expansion reaches a stand off we can then back fill these corralled systems.

This will enable the maximum amount of systems to be claimed peacefully.

Priority One – Explore the Hyperlane Network

The trick to the Star Corraling tactic is to know the geometry of the local network ahead of surveying and claiming. For example, if we know a whole section of systems is blocked in by our home system and the edge of the galaxy, then we can safely leave investing survey and construction time there until later.

For this reason our very first science ship should go out to explore the local hyperlane network rather start surveying straight away.

We also want to know as soon as possible where our competing empires are. It is in their direction that we want to expand first in order beat them to it.

Priority Two – Survey the Main Routes

Until we know what is in a system one system is much like another in terms of its resource yield. One system is not like another in terms of its strategic position. Systems which lead to access to more systems are to be preferred over those that are dead ends or in blind loops.

The systems which lead to more systems can be thought of as main route systems.

Priority Three – Claim the Bottlenecks and Choke Points

The reason for prioritising surveying the main route systems is to ensure we can claim them first. By doing so we naturally corral off from rival empires all the dead ends and blind loops that lie off the main route without having to spend resources actually claiming them.

Those systems on main routes that finally lock off access to the dead ends and blind loops are “bottlenecks” or choke points, which have defensive value in its own right.

Priority Four – Defensive Posture

Once our expansion begins to bump up against other empires we need to begin to prioritise defending our claims. At this point their future expansion will have to come from taking ours. It is time to start investing more alloys into active defence deterrents like ships and passive defence deterrents like starbases.

You could also start dropping unity into the Unyielding tradition at this point.

Priority Five – Backfill and Colonise

Now our borders are largely set and are defences are going up, it is time to start back-filling skipped systems and colonising the planets.

You might think that a REX should colonise early but I would say that is actually sub-optimal. Colony ships are very expensive and colonies take a long time to start yielding a ROI. The resources you spend on a colony ship could have been spent on several outposts instead. Remember about chasing two rabbits?

Reach furthest expansion and secure it before looking to colonise. Stellaris is a 4X game. REX constitutes the first two Xs, eXplore and eXpand. I would argue that for a REX strategy, colonisation should fall in the third X, eXploit.

System Skipping

Besides prioritising building outposts down the main routes, one might be tempted to skip systems to push out the boundaries of what can be peacefully claimed. One can do that of course but it is very expensive in terms of influence.

This is because the distant system’s influence cost is increased by each skipped system. But when you want to back fill you will still need to pay the influence on the skipped systems.

If you are rich on influence but short on alloys it might be worth it, especially if you have a fat discount on the outpost influence. For example from the Slingshot to the Stars origin and from being a fanatical xenophobe.

Otherwise the star corralling tactic above would be more efficient.

Tradition Sequence for a REX

You might think the Expansion tradition should go first. However given colonising planets is a lower priority than grabbing systems or surveying them, there is only tradition in that tree that is of immediate use.

That tradition is Reach for the Stars for a small discount on the starbase influence cost. That tradition is in line with REX priorities but is quite small and skippable if otherwise the Expansion tradition is of no interest.

Ideal Tradition Sequence

Adopt Discovery for Map the Stars Edict then take To Boldly Go for boost to survey speed. We need to survey before we can claim.

Then take either or both of Expansion and Domination to get Reach for the Stars (starbase influence discount) and / or Colonial Viceroys. Colonial Viceroys yields +0.5 to monthly influence which is arguably stronger and more versatile than the starbase influence discount of Reach for the Stars.

That is especially true if you are already rocking starbase influence discounts from being Xenophobic or having the Slingshot to the Stars origin.

Once you have some outposts and some mining / research stations you could adopt Prosperity for the boost mining stations and / or take the next Discovery tradition Databank Uplinks for the research station boost.

A proper REX will result in lots of systems but delayed colonies. Arguably then boosts to mining and research stations are better than boosts to colonies.

When expansion is checked by your rivals you can certainly expect they will be casting claims upon you. At about this time when you are prepping to defend, you could start down the Unyeilding tree.

After that, as you please.

Built to REX

Now we know how to REX, let us look at the empire builds that are optimal for REXing.

Ideal Empire Build Qualities for the REX

Government Type



Species Traits

Leader boosting traits are good for productive surveys and anomaly hunting.


The Ultimate REX Build

Rexer Build Summary

There it is, the ultimate guide to Rapid Early Expansion for Stellaris.

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