I feel your pain Glenn.

I have a similiar dilemma at the moment.
Playing as the English I have crusaded for Greece, initially taken the province with around 2100 men.
The Byzantines attacked back next turn with what only amounts to a hotchpotch army mainly consisting of broken Slav Jav and trebizond archers (around 9 units of archers) and were led by a 8 star 8 valour uber general Kata.
The tricky thing here is that he is only one horse the other 39 presumably died in another battle with the Hungarians and he sits well back out of arrow range and I cannot get to him.
I tried to get mounted crossbow to him but got cut to pieces by his trebizond archers and I could not get my infantry through either.
The Slav Jav and then trebizonds in hand to hand just decimated my numbers.
I dropped a good army with a 5 star prince into the crusade before hand and so had nice valour and full troops on the battle field but it was not enough.
My Fuedal Sargeants and FMAA were just destroyed.
I charged my heavy horse into the flanks nonetheless of his archers and did they rout, no they turned and cut down my horse like they were made of butter.
My prince died at the hands of an archer for goodness sakes.
All this because of a single Uber general that I couldn't even engage!
He had invaded with only 780 men to my 2100 and I managed to kill only around 450 before my whole army was routed and kicked back to Croatia
And this was me defending!!! Normally my stronger suite.