i tried something similar to having a military streangth counter for each country when working on alpha 3, but sadly wars just lasted forever and therefore ended up with the more simplified and random streangth system in alpha 3 as it's a lot easier to balance and have big changes in the wars happen while not lasting forever.
more complicated war sides and smaller wars will be added later on but want to wait until more info/data maps are done like subdivisions, ethnicities and cities
atm in alpha 3, it's 50% of either side in a 1v1 war having the advantage, and for the invaded by all event it is 100% of the invaded having a dissadvantage, but a 1 in 6 chance of it being a "controversial politician" event and therefore the one being invaded having the advantage, also during the events who got advantage do slightly change so it gives the overall advantage to the bigger countries as it takes longer time to invade and therefore have more time for the advantage to flip