Wow, maybe it's not an "historical" approach, but it certainly is unconventional and ingenious. RFRE purists might object that the marsh cities are supposed to be unconquerable so that they spawn hordes of barbarians in later years of the game, but as long as you put thought and effort into winning the game, and had fun in the meantime, then I'm all for it. But nevertheless we should "fix" this loophole in future patches. Pink, how about raising the defense value for marsh terrain to +999%? The Roman units cannot enter marsh terrain anyway, so this would not impact the game for non-creative types like me. Also, have each barbarian marsh city begin the game with a Wonder that conveys huge bombard defense to prevent someone from blasting the defenders with ballistae and catapults to soften them up prior to attacking via a road. (Whatever conveys bombard defense should be a Wonder, because if it is a normal improvement, it could theoretically be destroyed. Alternatively, if there is a way to have terrain confer bombard defense value, then raise marsh squares to the max).