---
title: "Build an army for Warhammer 40,000"
subtitle: "Compliance"
author: Seth
publish_date: 2025-03-14 08:00
date: 2025-03-14 08:00
hero_classes: text-light title-h1h2 overlay-dark-gradient hero-large parallax
hero_image: warhammer_space-marine-troops-by-games-workshop-1600x800.webp
show_sidebar: true
show_breadcrumbs: true
show_pagination: true
taxonomy:
    category: gaming
    tag: [gaming, scifi ]
---

There are so many possible armies you can build for the 10th edition of **Warhammer 40,000** that it can seem almost impossible to understand at first glance.
In this post, I decipher the rules for army building in **Warhammer 40,000**.

The first thing to know, if you're completely new to wargaming, is that wargaming exists outside of **Warhammer 40,000**.
I'm a 40k (and 30k) fan, so I'm not saying this to discourage you from buying into **Warhammer**, and in fact I think that **Warhammer** is one of the easiest ways to get into wargaming (it's what got me into it).
However, you also ought to know that you can alternately get into wargaming through other systems, like the books published by [Osprey](https://www.ospreypublishing.com/uk/osprey-games/wargames/), anything by [Mantic Games](https://www.manticgames.com/), and models from [Wargames Atlantic](https://wargamesatlantic.com/).
**Warhammer** offers a cohesive and comprensive inroad to the hobby, though, and so it is a valid destination.

Army building _starts on paper_.
Do not buy miniatures for your army until you know which miniatures your army needs.
Conveniently, building an army is essentially the process of figuring out what to go out and buy.

## Core army rules

The general rules about what makes an army start on pages 55 and 56 of the core rulebook for 10th edition of **Warhammer 40,000**.
You can't implement any of the rules listed on pages 55 and 56 with just the core rulebook, but it's still information you need to know.

It starts with one of the most important concept you need to understand about a wargame army: The size of a legal army is entirely arbitrary, and it's defined an imaginary Build Points.
For each unit of soldiers you add to your army, you "pay " some number of Build Points.
If you and your opponent agree to bring 500 point armies to the gaming table, then a 500 point army is legal.
If you and your opponent agree to bring 1000 point armies, then a 1000 point army is legal.

## Combat patrol

Before explaining the army building process, it's important to know that the 10th edition of Warhammer 40k has a game mode called **Combat Patrol** that makes building your army _really_ simple.

1. Buy the **Warhammer 40,000** core rulebook.
2. Buy a **Combat Patrol** box for your favourite **Faction**.
3. Buy or download the rules for your **Faction**

That's it.
In 3 easy steps, you're assembling, painting, and playing.

If you want more flexibility, or bigger armies than what fits into a **Combat Patrol** box, then read on.

### Choose a Faction

The next step is to choose a **Faction**.
The **Faction** you choose governs what miniatures and supplemental book you'll buy.

### Choose a Detachment

Next, at least according to the book, you choose a **Detachment**.
A **Detachment** is often tailored to specific units, so it may influence which units you include in your [as yet non-existent] army.
For instance, the **Brood Brothers Auxilia** **Detachment** for Genestealer Cults allows you to add some Astra Militarum units to your Genestealer Cults army, so you would need to purchase Astra Militarum units to make that **Detachment** work.

A **Detachment** also influences how you play.
For instance, the Adeptus Mechanicus **Rad-zone corps** **Detachment** gives you broad control over the battlefield by infusing it with fallout that potentially causes damage to your opponent's troops.
But the **Skitarii hunter cohort** Adeptus Mechanicus **Detachment** grants **Stealth** to all of your models with the **Skitarii** keyword, so you're able run boldly into battle with troops that are suddenly harder to hit than in other **Detachments**. 

It's basically impossible to make an intelligent choice of **Detachment** before you're familiar with how your Faction actually plays, but then again it's impossible to get familiar with a Faction without choosing a **Detachment**.

But anyway, the core rulebook doesn't list any **Detachments**, so for now this is just a requirement to remember later: Don't go to battle without choosing **Detachment** rules.

## Warhammer units

Step 5 on page 56 contains the broad core set of rules about what an army can and cannot contain.
An army in Warhammer 40,000 consists of _units_.
A unit is defined in a data card published in an army index or codex, and it might be just 1 really special soldier, or 10 infantry soldiers, or a tank, or anything else the Citadel miniature designers invent.
A unit always has at least 1 **Faction** keyword (such as **Adeptus Mechanicus** or **Adeptus Astartes** or **Heretic Astartes** and so on).
It also usually has several _general_ keywords, such as **Infantry**, **Transport**, **Character**, **Epic Hero**, and so on.

For each unit you include in your army, you subtract its Points cost from your total Point pool.
In other words, if you and your opponent have agreed upon a 500 Point army, and you add a **Character** unit costing 35 Points plus an optional 10 Point enhancement, then you have (500-45) 455 Points left to spend on more units.

Here are the universal army build rules:

* Each unit must have your **Faction** keyword.
* You must include at least 1 unit with the **Character** keyword.
* Only a **Character** unit may be given an Enhancement. Your army cannot include more than 3 Enhancements. No unit may have more than 1 Enhancement, and each Enhancement in your army must be unique.
* An **Epic Hero** may not have Enhancements, and your army cannot include the same **Epic Hero** more than once.
* For units with the **Battleline** or **Dedicated Transport** keyword, you may not have more than 6 units with the same datasheet name. For all other units, you cannot have more than 3 with the same datasheet name.
* A **Dedicated Transport** unit must start the battle with at least 1 unit in it.

That's all.
Now all you have to do is go choose which units you want in your army.

Units in your **Faction** are listed in the corresponding army _codex_ or _index_.

### What is a Warhammer index?

An index contains at least 1 **Detachment** rule set, and a datasheet for every box of miniatures that Citadel currently sells for your **Faction**.
Many indexes are available for $0 from [Warhammer Community](https://www.warhammer-community.com/warhammer-40000-downloads/), although they're removed when a codex for the same **Faction** is published.

### What is a Warhammer codex?

A codex is a physical book about a **Faction** in **Warhammer 40,000**. 
It contains lore, several choices of a **Detachment** so you can play to a specific strategy, special Strategems, a datasheet for every box of miniatures for that **Faction** that Citadel currently sells, and how many build Points each unit costs.

## Build a Warhammer 40k army

With the general rules defined in the core rulebook, and the datasheets in an index or codex, you can build a legal army.
To do it, you look through the datasheets of your **Faction** and choose the units you like and can afford given your Points target.

Each unit is described in its own data card, which provides its characteristics (Weapon Skill, Ballistic Skill, Toughness, Save, and so on), keywords and, most importantly for buying the right miniatures, the **Unit Composition**.
Usually found on the "back" of the data card, **Unit Composition** tells you how many models you need to create that unit.
Generally, **Unit Composition** is conveniently the same as 1 box of miniatures with the same name, but that's not always the case.
A unit of Skitarii Rangers happens to contain the same number of models as there are in the Skitarii Rangers box, but a unit of Kastelan Robots (sold 2 in a box) can have anywhere from 2 to 4 robots.

Write down each unit you decide you want in your army, and keep track of the Points you're spending according to the chart either in the back of the book or in the downloadable [Munitorum Field Manual](https://www.warhammer-community.com/warhammer-40000-downloads).
Stop adding units once you're out of points, or mostly out of points.
There are a few additional options, called **Enhancements**, that you might be able to spend some points on.

### Enhancements

The **Detachment** you choose for your army features **Enhancements** that, according to the core rulebook, any unit with the **Character** keyword may take at an additional cost.
There are some restrictions:

* Only a **Character** unit may be given an Enhancement.
* No unit may have more than 1 Enhancement.
* Your army cannot include more than 3 Enhancements.
* Each Enhancement in your army must be unique.
* An **Epic Hero** may not have Enhancements.

**Enhancements** range in cost from 10 to 50 Points, on average, so keeping your army just shy of your Points limit gives you a little flexibility here.

### Warlords in 40k

The final step is to choose 1 model with the **Character** keyword to gain the **Warlord** keyword.
Your **Warlord** doesn't get anything special other than the keyword, but your **Detachment** and its **Strategems**, or the **Mission** you're playing, may have special rules that mention the **Warlord** specifically.

### Buy miniatures

Once you have a paper list of all the units you want in your army, it's safe to go make your purchases.
These models are the ones you're going to assemble and paint and play with.
This is your **Warhammer 40,000** army.

## The difference between a collection and an army

You might notice that building an army isn't entirely linear.
There's a lot of uninformed decisions you have to make, like which **Faction** to play and which **Detachment** to use.
But how do you make those choices intelligently before you actually know how a **Faction** plays and how a **Detachment** actually performs on the battlefield?

Many players own more miniatures than they deploy all at once.
You might collect a bunch of Kastelan Robots, but only regularly deploy 2 to 4 of them, except for that rare game when you decide to play nothing _but_ Kastelan Robots (which you can actually kind of do, using the **Cohort cybernetica** **Detachment**).
You don't _have_ to collect more miniatures than you deploy.
You're free to buy just the miniatures you need for exactly 1 army using exactly 1 **Detachment**, or you can just buy a **Combat Patrol** box and use it.
But if this process has seemed complex and maybe over-flexible, the reason is that most players extract an army from a larger collection of miniatures lying in wait.
I don't think this is something you'd try to do right away, but I do think it's something that happens over time as you idly buy a model kit here and there.
It just starts to add up.
The good news is that you can reconfigure your army as often as you want, using miniatures that don't see as much action as others.