MIOs (Military Industrial Organizations) are the evolution of the old design companies, available only with Arms Against Tyranny. The key difference from the old system: you used to be limited to a single active design company per equipment category, while now you can run several MIOs of the same category at once, giving you a lot more flexibility to specialize your production.
What MIOs Are and How to Use Them
Every country starts with a handful of MIOs already formed, each specialized in a specific equipment type. A MIO can be assigned to three different tasks, and all three add funds toward its growth: as the designer of an equipment variant (applying its trait and policy bonuses to that equipment), as the manager of a production line (helping manufacture that equipment, at a cost of 0 
political power a day), or assigned to research a technology (giving a base +5% research speed bonus, extendable through traits and policies, for 0.1 political power a day while that research is active). Changing the MIO assigned to a design or a research project consumes army, navy, or air experience depending on the equipment type.
The 4 MIO Categories
Every MIO falls into one of these four categories, and each follows its own trait tree based on its specific specialty within it (for example, within Planes there are MIOs specialized only in fighters, only in bombers, or only in naval aircraft):
Material Equipment — artillery, infantry weapons, support equipment, vehicles, and other land equipment that isn't a tank.
Planes — fighters, bombers, naval aircraft, and close air support.
Ships — everything from carriers to submarines, depending on the fleet line you pick.
Tanks — light, medium, heavy tanks, and assault guns.
How They Grow: Funds and Cost
A MIO assigned to a production line earns 0.1 funds per production per day, capped at 100 funds a day. Assigned to research, it only earns funds once the technology is completed, in proportion to its base cost in days: a technology with a 110-day base cost gives 500 funds, one with a 165-day base cost gives 750, and so on. Because of this, if you want a MIO to grow fast through research, it pays to prioritize technologies with available speed bonuses rather than researching them ahead of time, since researching early doesn't earn any more funds for that technology.
The funds required to increase size grow with each level: 100 × (current size + 1)1.8 + 700. In practice, going from size 0 to 1 takes 800 accumulated funds, and reaching size 6 — the level where policies unlock — takes almost 11,000 accumulated funds in total. Each size increase grants 1 trait point to spend in that MIO's tree.
Traits: Irreversible Bonuses
Traits are a MIO's main source of bonuses, and every MIO starts with at least one already active. Each trait point earned from leveling up is spent in that specific MIO's tree, and once a trait is bought it can't be undone. Traits can be chained in a queue with shift-click instead of purchased directly, so they activate automatically as you earn points.
Policies: What Unlocks at Size 6
Once a MIO reaches size 6, it unlocks policies: an additional bonus that, unlike traits, can be changed later on. Assigning a new policy costs 25 political power, only one can be active per MIO at a time, and you need to wait at least 180 days since the last assignment before switching it. The full list is long and varies by category; these 4 are just an example of the ones available to any MIO, regardless of its specialty:
Ruthless Contracts — +10% funds gain.
Assembly Line Optimisers — +5% production efficiency cap and +5% to its growth (not available for MIOs specializing only in ships).
Vertical Integration — -10% production resources needed, but +10% to the penalty from insufficient resources.
Mechanical Genius — +10% reliability.
Beyond these, each category unlocks its own more specific policies: tank MIOs can get things like armor welding reinforcements or specialized casting, ship MIOs can get space-efficient hull designs or better handling in bad weather, and plane MIOs can get finishes that trade extra production cost for top speed. Some are even tied to a specific country or focus, like the one 
the British Raj unlocks after completing a particular industrial focus. It's worth checking each MIO's own policy tree instead of assuming only these 4 generic ones exist.
Common Mistakes
- Buying a trait just because it's available — some carry a penalty heavier than their bonus; check both numbers before spending the point.
- Not re-assigning the MIO as designer after unlocking a new trait or policy — the bonus doesn't apply on its own, you have to re-apply it to the variant and switch production over to it.
- Leaving a MIO unassigned to anything — with no production or research tied to it, it earns no funds, so it stays stuck at the same size forever.
- Sticking to a single MIO per category out of habit — you can now combine several at once, for example one focused on stats and another on production for the same equipment.