Monday, October 25, 2010

Statistics: How Many Bloodletters?

This week, I'm going to be writing a series of four articles looking at the troops choices for the four main chaos powers in Codex: Chaos Daemons in a similar way that I looked at the advantages of plague marines and noise marines in the past. Today, we're starting with Bloodletters of Khorne.Not so long ago, Raptor1313 wrote an article on how evaluating units by making their own points cost back is overly simplistic. So, what is it that I want bloodletters in my (mixed daemons) armies to do exactly? I personally think that the answer to that is to do what they do best: kill infantry quickly and efficiently. I'm not bothered if they don't make back their points. I just want to be certain that they do their job.

The situation.
Most commonly, I use bloodletters to take out squads of space marines. So in my considerations below, I will assume that I want my bloodletters to take on a squad of 10 marines. I will assume that one of the marines is a sergeant with a power fist. Perhaps one of the more typical set-ups that I come across is multi-melta plus flamer special weapons in these squads, so I will assume that as well.

In game terms, my bloodletters have to deep strike in. I will assume that this goes reasonably well and then I run them to ensure not too many bloodletters get whacked by templates and to get closer to their quarry. The marines will sit still and rapid fire them. After that, I will have my bloodletters assault the marines. (Of course, sometimes the marines may choose to charge them rather than the other way around, so this situation is necessarily simplistic!).

The question is this: how many bloodletters do I need to (statistically) achieve the goal of destroying the opposition (without having to rely upon them fleeing and the bloodletters catching up with them)?

The first step in this calculation is to determine how many wounds are caused by the space marines on the bloodletters before they can get in to combat. That's 8 rapid firing bolters, 1 flamer and 1 multi-melta. I'm going to assume that the flamer template hits 2 bloodletters (which may or may not be accurate in a real game - this is purely a thought experiment!).

How many hits do the bloodletters take on average from this volley? Firstly, there are 16 bolter rounds to consider. Two-thirds of them will hits -- meaning 11 hits (rounded up). We'll add 2 hits from the flamer, which makes for 13 strength 4 hits. I'm simply going to be pessimistic (from my bloodletter's point of view) and assume that the multi-melta also hits them.

How many wounds result from that? Well, half of the strength 4 hits will wound. That means approximately 7 wounds ... and we'll just assume the multi-melta causes a wound as well. So 8 wounds in total.

How many bloodletters survive? Their 5+ save is invulnerable, so they get a save from everything (just not a terribly good one). About 3 of those 8 wounded will survive.

For the win.
To fulfil my wants for the bloodletters, I must take out the entire marine squad in one round of combat. How many are needed?

The bloodletters on the charge have the benefit of the furious charge universal special rule. They're hitting and wounding on 3+. Moreover, they're killing on 3+ thanks to their hellblades. Moreover, they're charging, so they get 3 attacks each. That means 1.33 marines removed per bloodletter. I'd need 7.5 bloodletters to assure myself (statistically) that the marines would be removed entirely. Since they strike first (due to the higher initiative) the marines don't even strike back(!)

How many?
I lose about 5 bloodletters to the rapid firing marines. I need 7.5 to survive in order to wipe them out. Hence 5 + 7.5 = 12.5. Rounding up - this means about 13 bloodletters to achieve my aims. Although I will note that I've been pessimistic along the way (regarding the multi-melta which may not hit or wound, but I assumed it would!). Twelve bloodletters should be fine.

Shortcomings and caveats.
Of course, I've ignored the fact that sweeping advances could work just as well (against chaos marines!). Or if my opponent is near the board edge, they could certainly flee away and off the battlefield. And there could always be faults in my logic above! (let me know!). But overall, and from experience, I know that 10 bloodletters sometimes pulls up short, hence a unit of 12 or so bloodletters feels like it is about the right answer to my original question.


Atr_127 said...

just one thing, since you are working it out vs marines. dont forget that due to 'and they shall no no fear' marines never run if caught in a sweeping advance, they just take more saves.

jabberjabber said...

Hi Atr_127 -- Yes, you're right. I think my brain got stuck on chaos space marines.


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