Whenever I start to go into EU4 I end up ranting about it. I just deleted an essay I accidentally wrote while talking about the mechanics of actually warring. I'll just abstain from that. I think this topic is dead because there's literally nothing to do in EU4 aside from painting the world your color, and finagling and exploiting your way through the broken diplomacy and military mechanics.
See: The strategy on how to deal with a tiny one-province country, in places like Europe. I'll call this country A. You go to declare war, you mouse over the Call All Willing Allies. You notice all of your allies are on board but one. This one being a pretty major one, a big power broker in the area. For EU this is stuff like France, Britain, Sweden, etc. I'll call this country X. Why does X not want to help me over A? No reason, really. [I've usually got strong allies permanently at +200 opinion] Save the game and declare the war. This one NO on your 'call willing allies' will invariably join tiny, useless country A against you, a country they've been allied/married/had military access to since the inception of the game. This is typical in my cases.
How do you deal with this? By bribing, cajole the ally into taking a neutral stance on a war you're about to declare, as per history? No, there's no mechanics for this. It's simply a 'if the AI decides to fuck you, they can' design decision. So you, as the player, get to decide. Do you want to accept that you can never invade country A because country X will always betray you to help them? Or will you exploit your 'alliance' and declare war on someone they're rivalled to? We'll call this country B. Declare war, Have nation X join the war, and never put effort into finishing this war. Now X will be locked into not helping countries it guarantees/allys for all eternity until you end the war or they get a separate peace. This is an awesome design and not ridiculous, at all.
I also tried playing EU4 this week and quit as soon as I had something rad happen again. Declare a war on a vassal to another nation. Claim a province, or something. Call some allies in, even 1 will work. Now, occupy the vassal. Keep it occupied. Try attempting to occupy the overlord's land in any reasonable timeframe. Now, when your warscore reaches a certain point, your AI allies in your war will offer to this overlord country a separate peace [mind the separate]. This peace usually turns out to be a 'release vassal' peace. Now, mind you, I declared the war, occupied the vassal, occupied the overlord, and then, suddenly, I get a 'Peace!' popup, as if I offered a treaty to the other side. 'So and so [this being the vassal nation! The thing I can't even offer a peace to, and if I could, it'd be annexed as soon as I occupy it all!] has accepted our terms'. Now the vassal is released, and I'm still at war with the overlord and the original wargoal, the vassal, is independent, with a treaty with me. The fuck? You're saying random allies in a war like this can, and will fuck up your entire war goal, and even your plans of progress entirely? Why have allies in offensive wars like this then? I will provide any and all saves required to prove this situation is real.
This is the worst new-era release from paradox, atleast CK2 got fixed to a point of playability. EU4 is just... ugh, the battles aren't fun, diplomacy isn't fun, trading is moderately fun, colonization is so very dull, there's no flavor to anything. Even up to 1.4 I feel like my money was entirely wasted, as I still play EU3 to this day and actually enjoy it, as opposed to the ragefest of ridiculous mechanics and broken AI that is EU4.
Fuck. I did it again. I'm sorry, this was building up in me the whole time I was attempting to enjoy EU4 last week.