i finished my first iron man campaign, playing as byzantium.
all things considered it went better than expected, but i'm pretty disappointed with the end game, so i didn't manage to get all of italy and the last mameluk province. i went into war with brandenburg over bremen, thinking it would be nice to have a vassal up there. those guys were fucking monsters. they had low manpower and tiny armies so thought it would be no big deal, but they had like 115-120 discipline and almost 12 morale. what the fuck? they tore through my armies like paper. on top of that they were allied with austria and ferrera, so they managed to occupy most of my italian provinces and the balkans, with my warscore being over 50% in the red at its worst. the only thing that saved me here was the ridiculous AI: brandenburg split their forces and for some silly reason sent half of them all the way to jerusalem, where i had some scrub forces taking back provinces that some 3 unit stack that had landed in my africa had been taking.
when that happened i just spammed mercenaries in anatolia that was safe some of my fleet parked at the bosphorus with the rest blocking all of brandenburg (those idiots walked all the way around crimea to get to middle-east). contantinople was never taken, so when they came to siege it i could launch counter-attacks from adrianople. austrians and ferre..rans? rese? were pretty much useless and couldn't deal with with my armies, but if any of those stacks had brandenburgians they were almost untouched. just crazy. eventually they ran out of manpower and i actually recovered mine by using nothing but mercs. i got my warscore down and managed to call poland into the war, at which point even those freaks couldn't hold on. but that war lasted ages and as a result i ended up with ugly borders. poland also backstabbed me and made a separate peace, broke the alliance and turned hostile to me.
overall i don't think i was aggressive enough. it was my first iron man from start to finish, so i was a chickenshit most of the time and just tried to poach weaklings. also, somehow japan ended up as the defender of the catholic faith.