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.
The pioneers of the storming party attained the crest at 2 a.m.; and not until then was the alarm given to the dormant camp. The position, after a struggle which lasted but an hour and a quarter, was captured by De Wet, who, ere the midsummer sun had risen, was hurrying away with British prisoners of war, guns and wagons, which neglect of the ordinary precautions by a body of unprofessional troops had delivered into his hands.
At Rundle's Head Quarters, only three miles away, the sound of the firing had attracted attention, and a weak body of Mounted Infantry, the only mounted force at his disposal, was sent out to see what was the matter. It was unable to intervene with effect, and returned to report the situation.
The remaining detachment of Rundle's force, consisting of two companies of slow-moving Infantry only, was still further from his Head Quarters; but thirteen miles away in the direction of Harrismith lay a force of Colonial Horse. When a telegram from Rundle to summon them to the rescue miscarried, his staff-officer galloped away in the dawn and put them on the trail of De Wet; but he had had a long start and escaped into the hills near Bethlehem. Here he remained for a few hours, and then went towards Reitz.
During a temporary absence for the purpose of conferring with Steyn he left his commandos in charge of Michael Prinsloo, who on December 28 was engaged in a rearguard action with Elliott, who was conducting yet another drive and whom he easily evaded.
On the last day of the year De Wet disbanded his commandos a few miles from the spot on which he had assembled them at the end of November. In the interval he had evaded all the Elliott drives; he had captured a strong British post; he had marched without damage along the sides of a triangle on which lay the towns of Reitz, Lindley, and Bethlehem, each of which was from time to time in the possession of his enemy; and had never been more than thirty miles distant from the central point of the triangle. The captured guns were sent away beyond the Wilge River under Mears.
No blame can be imputed to Rundle for the unsatisfactory issue of the operations. He had little reason to suspect that any considerable force of the enemy was in his vicinity. He was engaged in mechanical work, the laying out of a blockhouse line. It was the immediate task before him, and to the best of his ability he used the untrustworthy and meagre instruments at hand. It would, however, have been more in accordance with military principles if he had employed his mounted troops in duties more suited to their arm, instead of holding with them the infantry position of Groen Kop.
Only a few days before, a similar misadventure had attended the construction of the Heilbron-Vrede blockhouse line. Rimington and Damant had hardly returned to Heilbron after Elliott's third drive when they were ordered out beyond Frankfort, to the assistance of the blockhouse builders, who were being worried by a commando under Wessels, which De Wet had sent out after the Council of War. Near the Wilge River they acted on a front too extended; and a portion of Damant's force was deceived by the slim tricks of a party of Boers working in cavalry formations and many of them dressed in khaki uniforms. In order to keep up the illusion they fired at detached parties of their own side, and in the end Damant was overwhelmed on a hill, with a loss of nearly 90 per cent. of casualties, before the rest of his command came up and drove away the assailants. Rimington was too far away either to prevent or to retrieve the disaster.
When the "drives" were renewed in the northeastern districts of the Orange River Colony at the end of January, 1902, the experience of the last few months had shown that they must be conducted on new methods. Hitherto the typical "drive" had been a net or nets cast too often hastily and at random, the meshes of which were large, irregular, and easily cut. The new "drive" was a bar of steel pushed steadily forward by simultaneous action throughout its length, and with its ends resting on the two completed blockhouse lines running eastward from Heilbron and Kroonstad.