Last week we talked about how to calculate and compare lethality of two different units. This week we will take a look at how to get a general idea of how long a unit will last for while under fire. This will be important when we later discuss how to compare different lists.
Each unit has a wounds statistic on their unit profile, but what I will be referring to as “effective wounds” takes into account their wounds, the model count in the unit, and their save value. Let’s work through an example. As always, it’s important to list our assumptions:
- The unit in question has:
- 10 models each with just one wound
- The unit will get its full save value
At the very least, it will take 10 wounds to completely kill this unit because normal damage doesn’t carry over model to model within a unit. However, because the unit gets its armor save, its statistical effective wounds is greater than 10. How much greater? Let’s take a look.
Formula 1 shows that to calculate effective wounds, we need to take the wounds of each model in the unit, add that to the wound of a model multiplied by the probability to pass a save, and multiply that by the number of models in the unit. Giving Formula 1 more detail we have:
So for our example, we can see our unit has 10 actual wounds, 15 effective wounds. This means that it will on average take 15 wounds to completely destroy the unit, despite the unit have only 10 wounds. How can we increase the mileage on this unit? For starters, we can try to get them in a position to receive a cover save. If this unit receives a +1 cover save, then their effective wounds goes up to 16.7. Not a game-changer, but it is statistically the equivalent to almost an extra 2 wounds, which as the game progresses might make a difference.
Another way you could increase the lifespan of a unit would be to stick them inside an open-topped vehicle that provides some protection from the ever-present dakka of the far and distant future. Let’s take a look at another example regarding Firewarriors and a Tidewall Shieldline. While inside of a Shieldline, Firewarriors are free to shoot as they please and benefit from the Shieldline’s decent 10 Wounds and 50% chance to pass a save (this results in the Shieldline also having 15 effective wounds). Each point of damage that the Shieldline takes does not reduce the firepower of the Firewarriors inside whatsoever. A unit of 10 Firewarriors plus a Shieldline is slightly less expensive than two units of 10 Firewarriors despite doubling the effective wounds of the Firewarrior unit.
What’s the takeaway here? If you assume that your Firewarriors are going to be shot at (decent assumption), and you want them to stick around, its better to purchase a Shieldline for them to ride in. You’ll have firepower that only starts diminishing halfway through their pool of wounds and if your opponent wants to try and destroy the Shieldline quickly with high AP reduction weapons, then all the better for your other high save units like Commanders, Ghostkeels, etc. that won’t be getting shot at by these high AP weapons. The Tidewall Shieldline specifically doesn’t blow up (only the Tidewall Defense Platform does) so your Firewarriors will be ok when it does finally bite the dust.
Now I’m sure there will be several of you that prefer the double firepower of two units of 10 Firewarriors over one unit and a Shieldline. If you can guarantee that you will get the opportunity to put that firepower to work (by having first turn perhaps) then by all means, that’s a great way to go. But I think we’ve all experienced getting a unit killed off the table before it had a chance to do anything. The Shieldline is a better way of keeping a unit around to deal damage while also dealing out the occasional mortal wound.
So there you have it, how to calculate a unit’s effective wounds.
Next time we will take a look at markerlights and what the pros and cons are to Tau’s various markerlight platforms. Spoiler alert – Pathfinders are great.
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