Create a single player skirmish with the following settings:
8 Players, no teams
Game Mode: Death Match
Map Size: Medium (4 player)
Immediately build 4-5 castles, some houses and some villagers to speed up building. When the castles are built, build some trebuchets. Your castles and the closeness of the map should bait your neighboring AI into building some trebuchets to attack your castles. Use this opportunity to lay down the hammer with your own trebuchets.