The difficult difficulty is difficult

In that difficulty, you better focus 100% on having an actual army instead of 3 footmen.

I didn’t play much in Hard, to be honest (I mostly “play around” with the game and modding than actually play, recently) but I must say that my successful Hard games were the ones I focused absolutely all my efforts on one thing: getting a Cleric as soon as I could.

also don’t try to raise your town value too fast… it will trigger the campaign faster
and try to micro your army to kill the weak ones first. that will lower the enemy dmg income faster