Actually you can and indeed it was done a number of times in WW2. The question is how far from your supply depots you can do so and the answer in Western Europe for US forces was over 300 miles. A rather meaningless sentence. Trains varied considerably in what they could carry as did trucks. In the case of US "deuce and a halfs" they could carry 2.5 tons off road or 5 tons on roads without overloading but the latter was fairly common. A US divison on the offense consumed about 700-750 tons a day. See: http://www.historynet.com/red-ball-express so you want supplies for over 18 additional divisions? Since your assumed quantity of trucks is not only questionable but rather obviously excessive your conclusions are irrelevant. Note also that it wouldn't be just trucks moving the supplies in any case. Clearly your example was rather far fetched but then that's not what we have been discussing either is it?