I can't beat the first mission in the French 100 years war

Its to damn hard! I barely beat the English 100 years war. Can someone give me tips on it. I get three then so many reinforcements for the enemy come and surround the last one. It is impossible to get through. Any tips on it?

-You have two units of chivalric knights and a unit of Royal Knights. Leave the RK alone.

-Wait a little while til English cavs move to the left side of the map but don't wait too long once your enemy has passed your gate. Then use your cavalries to destroy two ballistas on the right side of the map.

-Put you chiv sergeants, halberdiers and crossbows in front of your gate to distract your enemy.

-Once you've destroyed two ballistas march to the remaining ballistas. Don't let AI control your horses. Don't let them engage the marching English on the left.

Thanks. The problem is that by the time I get the first two three units of 100 Chrivilic Knights. They aren't stupid either. They don't follow you. And when one will the other two keep guarding it. Thanks for your help though.

When destroying two ballistas on the left side of the map (from your point of view), try to hold enemy cav (400 CK) with your infarty. Of course they'll not last long, but they'll give you time to move your cav away and destroy balistas (try to avoid combat; your mission is to destroy balistas, not to defeat the enemy army.

I guess I got lucky on expert: I just took my fastest units out and killed the nearest targets first. Some English knights made it to the gate but it was pointless.