Water, food coloring, cups, buckets, supervision.
Teamwork as well as strategy.
With two teams having “bases” at opposite sides of camp, they have a “well” of water that has been colored to match their team color. (food coloring red/blue seems to work) The kids then have one cup (but they can hold it in their mouth/shirt/boot) with which to transport as much of their water to the other teams “empty well”. If they are tagged/flags pulled and they are on the other teams side, then they have to dump all their water and return to get more water.
With 40-100 kids this can last upwards of 2 hours. Minimal supplies are needed, and the only facilitation needed is instruction and supervision.