18. For that day, therefore, as soon as the Greeks reached the villages and encamped, the Barbarians went off, having had the worst in the skirmish; and during the next the Greeks remained where they were, and collected provisions, for there was plenty of corn in the villages. The day after, they proceeded through the open country, and Tissaphernes followed, hurling missiles at them from a distance. 19. Here the Greeks found that a square was a bad disposition for an army when the enemy was behind them: for it must necessarily happen, that if the flanks of the square close together from the road being narrow, or from hills or a bridge making it necessary, that the heavy-armed men must be pushed out of their places, and march with difficulty,[157] being at the same time crowded together and thrown into confusion; so that when in such disorder they must be nearly useless. 20. And when, again, the flanks divide, those who were previously forced out of their places, must now of necessity separate, and the space between the flanks be left empty; and men who are thrown into such a condition must doubtless lose heart, if the enemy are behind them. Whenever, too, they had to pass a bridge, or any other crossing-place, each hastened on to get first, and the enemy had then a fine opportunity of attacking them.[158] 21. The generals, seeing that such was the case, formed six companies of a hundred men each, and appointed captains of these companies, as well as captains of fifty and captains of twenty-five.[159] These captains and their companies, on the march, whenever the flanks of the square closed together, fell behind, so as to cause no disorder in the flanks, and then led on outside the flanks; 22. and whenever the sides of the square opened, they filled up the centre, if the opening was narrow, by companies; if rather wide, by fifties; if very wide, by twenty-fives;[160] so that the centre was always full. 23. If, then, it was necessary to pass any defile or bridge, they were not thrown into confusion, but the captains and companies went over in succession;[161] and if anything was needed in any part of the main body, these were at hand. In this order they advanced four days' journey.