Production and construction get mixed up easily but they're not the same thing: production makes equipment with the factories you already have, construction builds the factories themselves, along with infrastructure and defenses. It's the queue that decides how much you'll grow, not how much you'll fight.
Why It Matters
Every civilian factory that isn't producing equipment or eaten up by trade is free to build: new factories, infrastructure, dockyards, forts, airfields, naval bases, or nuclear reactors. That's the usual trap for new players — pouring all your industry into tanks from minute one, without setting anything aside to build the factories that would give you more production a year down the line.
Construction Speed
Each construction line moves faster the bigger your construction speed bonus, which stacks technology, national spirits, some trade laws, and, if you have Arms Against Tyranny enabled, the temporary boost the international market gives you when you sell equipment. None of that replaces having more civilian factories — speed multiplies what you already invest, it doesn't stand in for it.
How Much You Can Build at Once
The number of construction lines you can run in parallel depends on the state's infrastructure level — the higher it is, the more simultaneous projects you can run without them slowing each other down. That's why raising infrastructure early in your industrial states pays off even though it's less flashy than rolling out a new military factory.
What's Worth Investing In
Infrastructure first in the states that already concentrate your industry — every level lowers the cost of whatever you build there afterward, so the spend pays for itself over time. Dockyards if you're building a fleet, forts on the border provinces you'll actually have to defend, and airfields or naval bases wherever you'll operate on a sustained basis. Nuclear reactors and special projects only pay off for large nations that already have their basic industry covered.