Add the following paragraph to the end of “Zones of the Wasteland”, immediately before the subrule “Expansion”:

Each Zone has a Development score, defaulting to the number of resources in that zone plus, if it is occupied, one. A Tribe’s Development score is equal to the sum of their zones’ development and three times their Weaponry.

Replace the subrule “Expansion” with:

At any time, a Tribe may gain control of a Zone that is adjacent to a Zone that they already occupy, if their Effective Strength for that Zone exceeds its Defence. To do this, the Tribe must remove a number of Resources from Zones they already control equal to the Development of the Zone they are gaining control of.