Toughest Campaign?

I think all campaigns are line what going mostly up and have some challenging missions, and you have your own horizontal line(call it "zero line") what is your items and generals(if you have good generals- strong , more then 4 - then its not so taught, as well as basic items on beginning like snare drum and warhorse and later fully equipted generals). So if mission line is highter then 0 then its really tryhard.

For me hardest mission was with Kate, Arnold, Dumouriez complete hre98 to get other princesses. After that other missions was taff but doable. in conquest I love 3 things:1. you are from beginning to final battle not a 'series' aka missions , 2. so I should manage resurces and attacks(ofc thanks to kanue for guide but anyway I had just 2(mostly) generals+1 trader and I REALLY hate when generals in missions are bugged(stay and don't move) like dummies(or even hostages) and you need to kill them to bypass. I would love to see less enemies but AI in campaign missions more like scenario conquest AI. That would be really challenging(!) and fun(!).But you can't wish everything.
I really like some missions when I had low on resurces and need build economy and train army to crush already formed army (like "battle of waterloo"(But I really love to play more realistic waterloo with many and many troops where you can't build and need defeat napoleon forces what charge similar it was in reality) or last coalition mission where you should crush france last time) emp eagle othervise had 'already given army' what in teory is right(because france already attack and other European counties many times make coalition and send troops ageinst Napoleon.).

So looking forward to lead next empire to world domination and hope in next campaigns will be smarter AI and less 'stand still' generals.

How exactly does regroupingwork I'm confused about how certain genrals get stars from it and others don't?

I see thank you ive never really got the hang of regrouping but now I have "key" of sorts

For me the toughest mission is imperial expansion on Turkey/russia eastern campaign.As a campaign it was very easy but i cant get past this last mission.as for campaigns im stuck on Eastern so i dont know the other 2 to have an exact answer

I disagree that SNS is the hardest campaign. I got 5 stars on most of the missions on my first try. I believe that Continental System in the HRE campaign, Retreat from Russia in IE, and Scorched Earth in EO were the hardest for me. Stuck for 7 months on the IE one. Oh, Waterloo as well.

I didn't have much trouble with Austerlitz. 3 Emperors was more memorable for me in a frustrating jaw grinding way.