How do you make the AI fight a battle in Map Editor

The AI just go scouting whenever I try to make the player fight a battle with the AI. The AI would not attack the player unless the AI unit is enclosed and has no choice but to attack the player's unit in front of it. How do I prevent the AI from doing this? I want to recreate battles like that one from the 1st mission in Dracula where you fight the usurper's army and the Hungarians near the end of the mission.