No further tactics? No special preparations to be made such as my combination of Ghengis Khan, the Greeks, and Sun Tzu? Well then...
You manage to hold them off just long enough to survive the battle and push them back, for now, but the war isn't over, and you've drained your coffers of most of your gold recruiting the mercenaries, and now they, too, are stricken with plague, putting an even further strain on what little food and medicine you have.