On the subject of Hordes and Mass Combat in Dungeon World

I want to be clear to note what I'm about to say may be in direct violation of the canonical rules established in DW for hordes:

I don't really consider Horde HP to be the HP of one monster, I consider it to be the HP of the whole horde, and evaluate HP bonuses based on how much space the members would take up as a rank and file unit (although they are often not organized that way).Considering that an apocalypse dragon has less than 30 HP; I don't have any problem with assuming a pile of small monsters that takes up as much space as a cart would have 7 HP or more than a house full of them would have 11 HP collectively. I also think battles could be fairly resolved in this way with a little tweaking.

• Armies are always huge. They have a minimum of 11 HP.
• Most of the time, even though the entirety of an army may not have armor the bulk of it usually has leather (with a few chains and plates here and there) so they always have +1 or more Armor.
• Though individual soldiers aren't always in the fight, they often cycle who is on the front lines.This qualifies them for Uncanny Endurace (Giving them +4 HP bringing minimum HP to 15)
• Its armaments are vicious and obvious (wicked looking pikes, swords, etc probably qualify. Hell, torches and pitchforks probably qualify): +2 damage (or you could probably upgrade damage to a d8)
• It organizes into larger groups that it can call on for support: organized, write a move about calling on others for help.
• It’s as smart as a human or thereabouts: intelligent
• It actively defends itself with a shield or similar: cautious, +1 armor
• It collects trinkets that humans would consider valuable (gold, gems, secrets): hoarder

Dealing 15 damage to a huge army doesn't mean that all members are killed, it means that it no longer forms a cohesive group. Individual members might run away, defect, be impartial merchants, and so on. Civilians might not abhor damage but nonetheless, non-professional soldiers roll damage twice and take the worst result.

On the subject of damage, DW says:

If multiple creatures attack at once roll the highest damage among them and add +1 damage for each monster beyond the first.

This is impractical for armies sized in the thousands. Or more accurately, it is practical for armies numbering in the thousands against just the PCs but probably not against roughly equal armies where one of them happens to also contain the PCs. When two armies are going at each other and the party is involved with one army, the damage of the opposing army is modified by adding the numerical ratio of one to the other as a whole number (2 to 1, 3 to 1, 4 to 1, etc). If players are not in an army, and yet face a Horde, its size ratio is also subtracted from their damage. Thus if an opposing army has a 4 to 1 ratio, the army gets +4 damage every hit, and the players get -4 damage every hit. Larger armies add this to their dice roll and smaller ones subtract it. This represents the fact that the overabundance of targets is sufficient that the individual players draw far less individual attention. 

Player Damage

It's obviously true that an army doesn't literally have 15 HP, and a player doesn't literally take out an entire army in one attack, but it's fair to assume that each exchange represents several minutes, and that the players actions on a microcosmic scale have tactical effects that amount to dealing damage. In other words, if you deal 12 points to a 15 point army, you didn't kill thousands of men on your own, you made them retreat from a key point, or something of that nature.