Maybe you used your bonuses poorly and didn't get enough industrial techs or the right army techs for the time period, so your industry and divisions are weaker than they should be. Maybe you didn't build enough civilian industry and your factory count is stunted as a result leaving you with an undersized army. This is a difficult question to answer without other info.

I have watched alot of videos of youtubers playing, advice videos but its Always the same thing. I love hoi4 and u wanna play it but its not fun when you cant win if you dont play as germany amd belive me im bored of germany. And the dame thing happens with 20,21,17. Then i know that if i let AI attack and if they lose manpower i would have easyer time beating its army but then the AI just does not attack. I played as hungary and united with austria, i got czehoslovakia and transilvania and than i finaly decide to go to war with poland and i had much biger army amd air superiority but when i push i just lose, i cant move a tile. I play as soviets and u cant push germany or Poland, i play as japan and i cant push china, with france or italy i cant push enyone. My problem is that my army just cant push. The only country I can win with is Germany and that is only if i play as nazis, as empire or democracy i cant win. I have been playing hoi4 for almost four years now and i still cant beat AI on easy.

What are space marines hoi4