Meanwhile, another failure to synchronise, and that a most grave one, was taking place miles away in the north with Clerfayt's command beyond the Lys. It is self-evident that where one isolated and distant body is being asked to co-operate with comrades who are in touch with the commander-in-chief, and with each other, the exact observation of orders on the part of that isolated body is of supreme importance to the success of the combination. _They_, all lying in much the same region and able to receive and transmit orders with rapidity, may correct an error before it has developed evil consequences. But the isolated commander co-operating from a distance, and receiving orders from headquarters only after a long delay, is under no such advantage. Thus the tardiness of the fifth column was, as we have seen, communicated to the fourth, and the third, second, and first, all in one line, could or should have easily appreciated the general situation along the Scheldt. But the sixth body, under Clerfayt, which formed the keystone of the whole plan, and without whose exact co-operation that plan must necessarily fail, enjoyed no such advantage, and, if it indulged in the luxuries of delay or misdirection, could not have its errors corrected in useful time. A despatch, to reach Clerfayt from headquarters and from the five columns that were advancing northward from the valley of the Scheldt, must make a circuit round eastward to the back of Courtrai, and it was a matter of nearly half a day to convey information from the Emperor or his neighbouring subordinates in the region of Tournai to this sixth corps which lay north of the Lys. Now it so happened that Clerfayt, though a most able man, and one who had proved himself a prompt and active general, woefully miscalculated the time-table of his march and the difficulties before him.