This battle appears easy enough to begin with. Use Alfred to take out the Knights to the east, and anybody else to destroy the Soldiers to the west. Then take everybody south. It's at this time that things get a little more difficult.

The Knights form the south will ride north to attack you. Once you've killed all the foot soldiers, Emily will appear at the north end of the map, and ride down ~ very ~ swiftly to attack you. You need to get everybody onto the land south of the bridge before she kills you.

If you want access to Scenario ?1, it adds another difficulty. You'll need to get someone to the hole near where the southern horsemen started. Then, you need someone to access the weed on the cliff edge across the bridge. If you're quick it's ok. If not, just leave a few units stranded about - Emily will be more bothered about killing them than chasing your more important generals.