I'd like to second this opinion. Conquering a city usually means big troop loss and one gets no reward, unless having the chance to collect lots of geos by keeping the city a long time. But defending the city might cost more than the income.Originally Posted by patrickf
I would not rise the city taxes significantly, otherwise the game would unbalance towards the top players. What about a pillage lot, a one time income after conquering the city? Alternatively, some defenders might surrender and become part of the new owner's army. Either way will encourage battle.