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From supposedly reliable intelligence, Abrams was able to follow the progress of troops and supplies south, and judge where and when the North planned to attack over the border into Vietnam. To paraphrase from A Better War, Lewis Sorley: Troops advanced south in waves 500 to 600, moving at 12.2 kilometers per day, mostly by foot, the trucks saved for supplies and ammunition. We were able to move perhaps 60 Kilometers on the unimproved section, partly because our load was not on our feet, but on our bicycle, and partly because we had no backup supplies; we had to get out of that jungle in short order.