The task before Warren was hard. In order to carry out Buller's plan he must cross an unbridged river and struggle through a country of which little was known. Next day two bridges were thrown over the Tugela above Trickhardt's Drift, which recent rains had made dangerous, and Hart's and Woodgate's Brigades were transferred to the left bank to cover the crossing: but it was not until sunset on January 18 that the entire force with its tedious transport was established on the north side of the river.
The mounted troops under Dundonald were sent out at mid-day to reconnoitre towards the N.W. and in the course of the afternoon his advanced squadrons came upon a Boer commando which was easily dealt with, but before the issue was decided, he had reported that he was engaged near Acton Holmes, and asked for help. Warren assumed that the mounted troops, which he had sent out to reconnoitre, had wilfully and prematurely forced on an action, and were now in trouble; and it was not until the next morning, after an infantry brigade had been moved out to support them, that Warren heard from Dundonald, whose previous messages had not clearly described the situation, that he was able to take care of himself. Dundonald had at first expected that the main body would follow him, and his reports seem to show that he had hoped to induce Warren to move towards Acton Holmes. He was rebuked for assuming, not unnaturally, that the objective of the operations was Ladysmith, and instructed that the objective was a junction with the other portion of Buller's force. He was summoned to Warren's headquarters and ordered to abstain from further attempts to ride round the enemy's right. Thus, as before at Hlangwhane, a promising cavalry movement by Dundonald was thrown away.
The deliberate march of the British Army from Frere and the delay at the Drifts gave the Boers ample time to prepare for the attack. On January 19, on which day Warren moved to Venter's Spruit three miles from Trickhardt's Drift, they were in occupation of the whole line from Vaalkrantz to the Rangeworthy Heights. Fourie was in command of the left, Schalk Burger of the centre, which included the important features of Green Hill, Spion Kop, and the Twin Peaks; and L. Botha of the right, in which was Bastion Hill.
There were two roads by which Warren could advance; one running by Fairview northwards from Trickhardt's Drift between Green Hill and Three Tree Hill, and the other eight miles longer by Acton Holmes. The length of the latter and a report from White that several commandos were on their way to Acton Holmes from Ladysmith, led Warren to adopt the former route.
He informed Buller of his decision, adding that certain "special arrangements" which he had made would oblige him to remain near Trickhardt's Drift, and that he must therefore have further supplies. The "special arrangements" were in fact the steps which every general would take before attacking a strong position not immediately accessible; namely to acquire ground from which it could be threatened and shelled. Clery was ordered to direct the operation, which Warren believed would entail "comparatively little loss of life."
Early on January 20 Clery with one brigade and artillery advanced up the re-entrant which springs from the river towards the east end of the Rangeworthy Heights, and posted his guns half way up the valley on Three Tree Hill. Hart, with a brigade of five battalions, was sent to occupy the irregular southern crest of the heights running from Three Tree Hill towards Bastion Hill. He drove the Boers out of their advanced trenches, but found that the northern and higher crest to which they had retired, could only be won by a frontal advance across open ground. He and his brave Irishmen were as ready as ever to push on in the line of the greatest resistance, but he was ordered by Clery to forbear. Meanwhile Dundonald, not deterred by the damping of his trek on the 18th, and while obeying an order from Warren to come to heel, seized Bastion Hill, thereby securing Hart's left flank on the crest. So far as they went, the operations of January 20 were successful. Warren's pivot movement was in train, the whole of his force was now threatening the Boer right which was widely extended but deficient in depth; and the day's casualties were few. Following the example of Buller, who delegated his authority to Warren, the latter entrusted the conduct of the day's operations to Clery, who in succession ordered the chief movement to be carried out by Hart. Next day the mounted troops on Bastion Hill were relieved by infantry.
Buller was aware that the Ladysmith garrison, weakened by sickness and privation, could give him little or no help; but at least during the earlier phase of the Trickhardt's Drift operations he was confident. On January 17 he told White that "somehow he thought he was going to be successful this time," and that he hoped to be within touch of Ladysmith in six days. His Head Quarters were at Spearman's Camp, a few miles south of Mount Alice, whence he rode over daily to note and criticize the tactics.
It now occurred to Warren that he might have been mistaken as to the significance of the position occupied by the enemy on the Rangeworthy Heights, and that it might be in reality a screen to hide a trek of the Free Staters back to their own country; and on this supposition, which was founded upon reports that the Siege of Ladysmith had been raised and that some wagons had been seen on trek westwards towards the Drakensberg passes, he applied for reinforcements to enable him to block the way.
Buller sent him Talbot Coke's brigade with some howitzers; and came over to consult with him on January 22. The situation was not satisfactory. Time was being wasted, Warren's "special arrangements" had done little, and now he had a new idea. Buller still advocated an attack on the enemy's right, while Warren wished to persevere with his advance by the Fairview Road; but he pointed out that Spion Kop, which his reading of the "secret instructions" had led him to regard as out of bounds, must first be taken. No definite action seems to have been decided on, and Warren was left to act within certain limits on his own responsibility. Finally, with the approval of the four infantry generals, he resolved to seize Spion Kop that night. The attack, however, was postponed until the following night, to give time for the position to be reconnoitred.
Spion Kop is a ridge of which the chief features are a pair of high peaks joined by a nek to a plateau, from which a spur, ending in a kopje called Conical Hill, juts out at right angles to the nek, which becomes a spur of the plateau at a Little Knoll east of the summit. Its tactical importance was derived from its height, as the summit, though not the peaks, is higher than any of the ground held by the enemy; and from its position, as it was on the obtuse angle formed by the meeting of Botha's line on the Boer right with Schalk Burger's on the centre, and enfiladed each of them. It was accessible from the British front by a slope which rises from the lower ground to another spur running S.W. from the plateau.