During the Seven Weeks War of 1866, railways enabled the swift mobilization of the Prussian Army, but the problem of moving supplies from the end of rail lines to units at the front resulted in nearly 18,000 tons trapped on trains unable to be unloaded to ground transport.[12] The Prussian use of railways during the Franco-Prussian War is often cited as a prime example of logistic modernizations, but the advantages of maneuver were often gained by abandoning supply lines that became hopelessly congested with rear-area traffic.[