I've got over 1,500 hours in this game, and something bugged me within the first few of them: the AI never really weighs its decisions. It follows the historical script whether or not that script still makes sense in the game it's actually in.

Take Japan. As a player you quickly notice you never actually need the historical Pacific war. There's no oil crunch forcing your hand, so why would you ever bomb Pearl Harbor or tie up divisions occupying the Philippines? China folds without much trouble, and once it's done, the obvious next target is the USSR, which is a far softer and more valuable prize than starting a naval slugfest with the United States. But the AI marches down the historical path anyway, straight into a war it's basically doomed to lose.

And the frustrating part is the historical path isn't even fully wired up. Historically, Pearl Harbor is what dragged the US in, and Germany declared war on the United States four days later (11 December 1941). In game you rarely see that whole chain actually fire: Germany doesn't reliably declare war on the US, and the US doesn't reliably commit against the European Axis. So Japan eats the entire downside of the historical path (waking up the US) without the historical consequences that made that gamble make any sense in the first place.

The guarantee system makes this worse. Classic example: if Germany stalls, the Soviets roll into Poland, and because the UK guaranteed Poland, the Allies end up at war with the USSR. That's a disastrous outcome for the Soviet AI, and it isn't even how it went historically. The British guarantee to Poland had a secret protocol limiting it specifically to German aggression, which is exactly why Britain and France did NOT declare war on the Soviet Union when the Red Army invaded eastern Poland on 17 September 1939. Halifax flatly told the Polish ambassador the obligation only covered Germany. The game treats guarantees as a blunt, unconditional trigger, so you get ahistorical wars and the AI getting dragged into fights nobody actually benefits from.

Same energy with the rest of the diplomacy AI: the UK barely reacts to fascist expansion, won't guarantee nations already in a faction, and so on. To be fair, Paradox is clearly aware. The latest patch made the UK less likely to pick the faction rule that lowers the tension needed to guarantee nations on historical, and Pearl Harbor's success chance got reworked too. But the core problem is still there: the AI does the scripted thing whether or not it serves its own interests. It's the whole "just because you can, doesn't mean you should" issue, except the AI never asks the second half of that sentence.

So where's the line supposed to be? How much historical railroading do people actually want, versus an AI that reasons about consequences? I doubt we'll ever get genuinely decision-based AI in HoI4 (maybe that's a HoI5 dream), but at minimum the guarantee system feels like it badly needs a rework. Curious where everyone else lands on this.