Thank you for your assistance, but it ended up a damp squib. I deployed stakes everywhere I could, positioned by meagre infantry around the gate, set my treb to fire rotting cows, pressed start then raced by longbows and yoemen to the walls.

The Mongols in their infinite wisdom did not fire a shot with their artillery, but came at me with seige engines. As you would expect my towers and archers opened fire, I landed a cow in their line of advance to the gates and once they broke through several hundred horses from the 2 stacks threw themselves on my stakes rather than walking through.

Result 2 more dead 9* generals, Mongol losses over 1000, my losses under 250 (their towers made it to the walls). I even managed to sortie at the end and capture the Trebuchet crews.

I captured Jerusalem 5 turns later thereby extinguishing the Mongol threat.