Requesting Feedback on my Mass Combat System

One of my dreams as a DM was to one day have an epic war scenario where huge armies clashed. Well, last month I finally got that opportunity. The party recruited an army of jungle tribesmen and lizardfolk to take part in a 4-way war to claim the ruins of ancient city. When it became clear this was the direction we were heading, I quickly realized that I needed a fast and simple way of handling hordes of miniatures and started testing out some different mechanics - borrowing a bit from my very limited experience with warhammer. I knew there were three things I wanted:

1. I wanted the players to control their allied army
2. I wanted to group miniatures into units, typically using trays like pieces of cardboard to keep them together.
3. It NEEDED to be FAST and easy to run.

This is what I came up - I think it was a huge success. Combat was lightning fast, simple, and I could run the entire game while only referencing a single sheet of paper, some mini D6s, and a single D20. It was also easy to homebrew new types of units on the spot if I needed to. Most importantly, my players seemed to love it. That said, I think there is plenty of room for improvement so I'd love to hear opinions. I should also note my goal here was mainly for tabletop play with tons of physical minis - I haven't even thought about how I would translate it to a VTT.

Here's what I came up with:

Core Concepts:

• The player's PCs still use normal combat rules
• Each army is divided into units. A unit is a group of minis on a tray acting together. Sometimes units can be solo miniatures (like giants or siege engines), but the core mechanics remain the same.
• Both allied and enemy units track health in Wounds instead of HP.
  • 1 Wound = 15 damage (this is the number I came up with which felt right for my level 9 party, but I think it could easily be scaled down to 10 damage or 5 damage if necessary).
  • Sometimes we track Half-Wounds, which equates to anything less than one full wound. If we need to convert a half wound to damage, we treat it as 7.
  • More on Wounds later.

Unit Statistics:

• A unit typically has the same stats (including skills, speed, saves, movement, to hit bonus, and AC) as the individual creatures that make it up. If the unit is comprised of different miniatures, I usually use the stats of the majority.
• There are three notable new statistics:
  • Health (Wound Threshold or WT): Each mini in a unit tracks health separately in the form of Wounds. A standard soldier or zombie for example, has an WT of 1 Wound. A goblin might be a half wound. Typically I give large minis an WT of 2 wounds, huge minis a WT of 4 wounds, and gargantuan 8 or more. However, this can vary based on the creature. When a mini suffers wounds equal to or greater than its Wound Threshold, it is removed from the tray.
  • Damage (Wound Output or WO): The amount of damage in Wounds each mini in a unit can inflict. I gave standard soldiers/zombie units a WO of 0.25, large units a WO of 1, Huge units a WO of 2, and Gargantuan units 3 or more. Again, this can vary based on the creature.
  • Total Wound Output (TWO): You add together the Wound Output of each mini in a unit to determine the unit's TWO. This is the amount of damage the unit can inflict.

Wounds and Damage:

• When a PC attacks a unit and hits, they roll for damage normally and then divide the amount of damage they inflict by 15. For every whole number, they inflict that many wounds onto the unit they hit. I add an extra half wound if they don't quite reach a multiple of 15. If they don't do at least 15 damage, they inflict a half wound.
  • The attacker chooses how to distribute the Wounds they inflict, and they can be distributed among multiple minis. For example, if they do two wounds in damage against a horde of goblins with a WT of 0.5 wounds each, then they can kill four goblins with one hit.
• Where necessary, I track wounds with miniature colored D6s. I have one color for a full wound and another color for half wounds. If I need to track damage, I place a die on the miniature's base. I often saw scenarios where every mini a unit suffered a half wound or a full wound (typically from AoE), so in the future I might use different indicators specifically for that.
• When a unit attacks a PC, the wounds or half wounds they inflict are converted to damage. 1 Wound = 15 damage. Half Wound = 7 damage.

Attacking Rules for Units:

• (I actually have tweaked this part of the rules since the last time we played, so I haven't yet tested the modified version)
• A unit's To Hit bonus is based off the To Hit Bonus of the individual creatures comprising the unit.
• Each unit gets multiple attacks, calculated as:
  • For each mini in the unit with a WO of less than 1, add up their WO and then round down. They get that many attacks. Each successful hit does 1 Wound.
  • For each mini in the unit a WO of 1 or more, that mini gets its own attack. Each successful hit deals damage equivalent to that mini's WO.
• If a unit's TWO equals less than 1, they still get an attack but deal a Half Wound on a hit.

Ability Checks for Units:

• Units roll ability checks and saves as a group (see their stats).

NPC vs. NPC (Speed Rule)

• Unless the DM says otherwise, NPC units auto-hit other NPC units and inflict damage equal to their Total Wound Output.

• Once the player's got the hang of the system, this helped the game flow tremendously.

Clash Reaction (Speed Rule)

• (This is a rule I'm not too sure about, and only tested in one of our battles - I could take or leave it).

• After an NPC unit is attacked in melee by another NPC unit, it can make a melee attack as a reaction (which they can only do once per round). Again, the attacks auto-hit.

• Helps reduce the number of minis on the field faster, keeping the game going fast.

Movement:

• We used rulers to move minis about the map. 1 inch = 5ft. I was pretty lenient with this to keep things moving.

• Units can dash to double their movement.

• As far as moving units through other allied units, I tried both disallowing it and allowing it. I found that the former led to some frustrating moments for the players as some of their units became stuck behind their allies and could do nothing.

AOE Damage:

• This is a big one. Early on we found that AoE was incredibly powerful since it could deal simultaneously to EVERY mini in the area of effect instead of a standard block of damage that is distributed amongst the unit. The players called it a delete button. Ultimately we decided on the following rule:
• Damage inflicted by AoE Spells is Halved, and then converted into Wounds. So if a fireball does 32 damage, we half it to 16 and then convert that into 1 Wound. Every mini in the fireball's area of effect (regardless of what unit they are in) suffers a Wound on a failed save (still rolled as a unit) or a half wound on a pass.
  • If, after being halved, the AoE spell calculates to less than 15 damage then it does a half wound instead.
• Thinking back on this, maybe I jumped the gun on applying this rule? Maybe it wouldn't have been so bad to keep AoE damage as is? I could have allowed the players to continue to feel powerful with their AoE, but find other ways to challenge them - like sending hordes of reinforcements to replace the ones they mow down or putting units with beefier creatures in their path.

Healing:

• When a unit is subjected to healing, the healing must target a single mini unless the spell allows multiple targets.
• Every 15HP of healing done restores 1 Wound.
• If less than 15HP is healed, they are healed by a half wound instead.
• Minis that have fallen to 0 wounds and removed from their tray can be brought back when they are subjected to healing - as long as the entire unit has not been annihilated.

Special Features:

• Some creatures have special abilities to help keep combat diverse and engaging. Some examples:
  • Zombie units that explode when killed, dealing AoE damage to anyone in range.
  • Flying Dragons with AoE breath attacks
  • A Zombie-Trex that can disgorge another unit of zombies, and a colossal corpse golem that can toss units of zombies great distances.
  • Anti-Cavalry units that discourage charges
  • Siege weapons and archer towers
  • Siege units designed that deal extra damage to objects and structures
  • Titans with immense power that serve as battlefield centerpieces

And that's the gist of what I have so far! It took a bit of explaining, but once the players got the hang of it the game flowed smoothly.

My Experience:

• All of my battles so far (we've had three) have been offensive in nature. I set up a battlemap with an enemy stronghold or defense point, give the party objectives to complete (that aren't just annihilate the enemy) and set a starting line where they can begin deploying their units. I feel like they really enjoyed the deployment phase. I don't know how well a defensive or neutral scenario would play out yet.

• I'll break down the three scenarios I've run:

• Stop the Goblin Ritual (test run): Goblins had made camp around an ancient shrine and were conducting a ritual to summon a powerful titan. The party led their army to attack the camp , taking down watchtowers and busting down defensive walls, and then had to defeat the goblin shaman before the ritual could complete. I honestly threw this one together on the fly so we could test run the system.

• The Thayan Gate: After a skirmish with a Red Wizard scouting force, the army tracked them down to their base of operations only to discover they had constructed a massive gate powered by the necrotic energy generated by two titanic zombie sauropods. The Red Wizards were in the process of summoning a colossal army from Thay - after a number of rounds, the portal opened and waves of skeletons and undead siege units began to pour into the battlefield. They needed to take down the sauropods before the endless hordes of skeletons overwhelmed them. There were side objectives too that they could accomplish without taking down the Sauropods, but I won't get into that.

• The March of Thunder: A superweapon is hidden in a dungeon beneath the ruins of an ancient city - the party must get to to the dungeon and stop the superweapon before it ends the world. However, an army of Yuan-Ti - supported by endless hordes of zombies - refuse to let this happen. The army must escort the party through the city and reach the dungeon, all the while being bombarded by artillery, hordes of undead, and Yuan-Ti trickery. I broke this up into phases representing each section of the city they reached with different challenges they had to deal with in each phase. The army dwindled as they made their way through each checkpoint.

I really want to run more scenarios using this system, though I'm interested in getting outside opinions on it first. Are there obvious flaws I'm missing? Have I simplified it too much (or not enough) in my effort to make it fast and easy to run?