Most tacticals last at least 24 if not more, hours. Have established rules and judges who understand how they work. A suggestion is to use some form of communication system to coordinate between the marshals thus alleviating some of the confusion and stopping the event. A Parliamentarian complaint was a lack of action on the part of the Royalists. Defenders aren't obliged to attack.
Forts tend, by their very nature, to turn even aggressive forces passive.
If the forces are unequal, the smaller force should be given the fort. Attacking forces should be atleast twice the size of the defenders. This would disallow any unfair advantage from the outset To make the defending force aggressive objectives may be weighted so that holding just the fort would not in and of itself constitute a victory. This is usually reserved for those events where one side is numerically on a par with the other but lacks leadership, experience, or is in some way inferior to the other. Disallow children to participate in the role of a soldier.