From how I’ve tried many times, the initial battle on Ismail 4 seems not possible.
Many people already said that the battle is not that hard, but compared how I felt, I think the scenario may have unintentionally changed a bit…? Because sometimes a game update unknowingly affects campaign A.I.s.
I’ve tried both direct breakthrough and defeating them little by little, but neither of them helped me.
Even killing Shaybani Khan early doesn’t help a lot, because there’re too many enemy units. Even after killing him, the remaining enemy units still overwhelm me by outnumbering.
I don’t think the Ismail campaign itself is hard, but this part on the scenario 4 looks somehow unfair though it would’ve been fine before or during tests.
I have not played the map but hopefully I can help you.
My general strategy for single player campaigns is using the pause button to help me micro better. Try wall yourself in, and establish a defensive position. Try use monk mechanics to convert new units and heal units. Try secure an enemy market so you can use it for trade, with an influx of gold from 10 trade cards you should be able to produce more gold intensive units and be able to overpower your enemy.
In certain scenarios enemies start off very weak, try rush them and weaken them.
It is doable if you micro properly and understand the basics of hill advantage, cavalry tanking and kiting.
It’s a bit at the limit (on Hard difficulty), but I had to retry it only once before succeeding.