i am moving more to instead of half unless thats simpler to program durability should work like this

for every 10% of your total maximum HP you lose in a battle you lose 1 durability.
SO every time you die you will have lost a total of 10 durability. Meaning you have to DIE 10 times to be out of gwf - Instead of win 20 times.

The power buffs should only be 5% per city