I'm curious how the game will reflect how wars were fought starting from the industrial revolution to now. Such as aircraft, changes to navies and ground forces. Will there be a period where warfare reflects WW1 and later WW2? What about warfare during a cold war era? Things change quite a bit from massed formations of riflemen to trenches all the way to combined arms offensives and part of me is worried that technology will move too quickly to appreciate such times and change our strategies to fit our technology. I've run into the issue of unlocking a unit of a certain era and by the time I produce and army of this particular unit or units they are already obsolete by a mile while playing Civ and Humankind and Civ are compared often due to them basically competing now.

 Basically I'm curious if this will end up like civ, and if warfare will be reflected in a more proper way. Such as the evolution of artillery, gatling and machine guns, riflemen going from muskets to bolt actions or repeaters to assualt rifles, aircraft starting out as war balloons/zepplins to biplanes to monoplanes and finally jet fighters, you get the idea. Wars in the current shown eras using melee weapons and arrows works fine with the current system but what about later eras and will we be able to fight those wars a satisfying amount? Not deploying an army of musketmen to suddenly find out in 5 turns you'll have semi modern riflemen.

I apologize for rambling but hopefully you guys will have ideas on how to implement ideas regarding this topic without them being too development intensive and take away from other aspects of the game.

In-game I would advise that, except for the Industrial Era, unit Combat Power never increases by more than ~25%.

Some more difficult steps would involve the industrial and social supports needed to field modern armies. This would probably involve a bigger role for pops in both armies and industry or science production. There should also be bigger impacts for combined or supporting arms on the battlefield. So for example, an infantry attack or an artillery bombardment would both do little damage, but combined they would do much more damage.

random thought, but how will resource requirments be handled for units that historically relied on coal, oil, or a fuel derivitive. should it be a set amount for creation of the unit or a turn by turn cost for a limit on the amount of units a certain nation can field. it would also be kinda cool if a nation had large coal reserves but hardly any oil and could invest in a synthetic oil derived from coal like germany did during the second world war

Reliance on late game resources like coal and oil for fuel could be shown not only in requiring those resources to produce the unit, but increasing penalties over time if you lose access to the resource. For example let's take a tank unit that requires oil for fuel in its engine. Let's say it requires 2 iron and 2 oil deposits to produce. If you lose access to the oil deposits it could gain a stacking penalty to its combat strength over time, similar to how stability isn't a straight drop and instead decreases or increases over time, to show the reserves of the platoon or military as a whole depleting and becoming unable to operate at peak efficiency. If you lose access to your iron deposits perhaps your tank platoons will no longer passively regain health in friendly territories?

Of course systems like that would make it really hard to come back in a war if you lose access to those resources, which might be a point for historical accuracy but definitely a penalty on the fun factor.

Based only on Scenario 1, it seems like units will be treated like they were in Civ5, where the resource is needed to produce the unit, and there is a combat penalty (-25%) if there isn't enough of the resource. There's no sign currently of a "stockpile" mechanic like there is now in Civ6.