Elliott's units then returned to their respective bases to refit. A column under Dartnell at Bethlehem, which had recently been reinforced from Rundle's command by a strong detachment under Barrington Campbell, was on the point of returning to Harrismith, when it was informed that De Wet's re-united commandos were lying in wait at a spruit about twenty miles out on the road to Harrismith. Dartnell marched on and maintained himself without much difficulty when he arrived at the spruit. Campbell came up, and De Wet's commandos withdrew without orders; but no attempt was made to convert their retirement into a rout. Dartnell continued his march to Harrismith. After the affair at the spruit De Wet again dispersed his burghers, with orders to hold themselves in readiness to muster at short notice. He had not long to wait before he saw another opportunity of employing them. A small force, less than 1,000 strong, was covering, half-way between Harrismith and Bethlehem, the construction of the main blockhouse line to Kroonstad, under the personal superintendence of Rundle. The force was broken up into three detachments, which were too far apart to render each other effective support in case of a sudden attack. The strongest detachment, consisting, however, entirely of Yeomanry, was posted on Groen Kop, three miles distant from Rundle's Head Quarters. The position is fairly strong, and resembles a wedge lying on the veld, with a gentle ascent from the east to a plateau to which the normal level rises steeply on three sides. A mile or two to the S.E. it is commanded by a higher eminence, from which a party of Boers had already been expelled. It was not, however, occupied, and De Wet promptly made use of it as an observation post, for which it was admirably adapted, as it looks down into the British position on Groen Kop. Moreover, the customary movements for protection, such as the relief of outposts, were carried out with such extraordinary laxity and neglect that De Wet was soon able to acquaint himself with almost every detail of the defence. Even the emplacements of a field gun and a pom-pom were disclosed by shots casually fired for range-finding purposes. On Christmas Eve De Wet saw that he had before him a prey that would fall into his hands as easily as Sannah's Post or Waterval Drift, and he resolved to clutch it at once. His burghers, though dispersed, were within call, and a force of over 1,000 was quickly assembled. With unerring instinct he selected the steep N.W. corner of the Groen Kop wedge as the point of attack, reasoning that the defenders would think themselves adequately protected in that direction by the nature of the ground. On Christmas morning, soon after midnight, over 1,000 Boers were in position under the broad end of the wedge. They were not discovered, as no patrols had been sent to watch the ground beneath, and the sentries on the crest gave no sign.