well because the supply wagons are so slow without it that they usally get left behind when i move the army ahead. I usally try to stay away from the 3rd city and try to attack the 2nd city or the captial so i have to move my troops further than usual you can see why its so useful to me plus the extra hp doesnt hurt either
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Kids, you tried your best and you failed miserably. The lesson is, never try. -Homer