The Boers on the Biggarsberg at first numbered about 15,000, but by the end of March many commandos had been attracted away by Lord Roberts' advance to more strenuous fields. Some time passed without any definite action having been agreed upon between Lord Roberts and Buller. The latter objected to almost every proposal made by the former, and sometimes even on reconsideration criticized his own proposals. He was allowed to recall the Vth Division, which after a brief absence rejoined his command; but even with it he protested against an advance on Van Reenen's Pass, which he had himself proposed and which he was instructed to make at the beginning of April, because Lord Roberts would consent to the employment of one division only in it. Lord Roberts did not insist on the movement, as Buller now said that it would endanger not only his own force, but also Natal; and finding that Buller had far more troops than he could usefully employ, ordered him to send the Xth Division under Hunter round to Kimberley. Even after its departure Buller outnumbered the enemy by more than five to one.

He was still haunted by the troubles of the Tugela, and was unable to nerve himself for the risks that every leader must run. The Boers bewildered him. He could plan no scheme without a conviction that somehow their "knavish tricks" would frustrate it, and his inactivity made him more prone than ever to brood over possible mischances. He remained in Ladysmith because it was the only course open to him after he had by a process of elimination considered and rejected all the alternatives. Each of them had its disadvantages and its dangers, therefore it were better to stay where he was. During a critical period the Natal Army was of as little use to Lord Roberts as were the Spanish contingents to Wellington in the Peninsula; and its laggard action retarded the progress of the war. Lord Roberts laid his plans for the advance on the assumption that it would be in operation on his right flank when he reached Pretoria, and if L. Botha had found it pressing on him when he was playing at peace-making in June, instead of engaged in equally fruitless negotiations with his brother 180 miles away at Laing's Nek, it is improbable that he would have continued the struggle.

On May 2 Lord Roberts informed Buller that he was ready to start from Bloemfontein, and that he expected the Natal Army to co-operate with him by attacking the Boers on the Biggarsberg, and then advancing towards the Transvaal. For this movement Buller considered that his force, which consisted of three divisions of infantry and three brigades of mounted troops, in all about 45,000 men, was insufficient; but he proceeded to carry it out. The Boers were in occupation of the whole line of the Biggarsberg from Helpmakaar westwards, and commanded the roads as well as the railway running through the range.

Buller on this occasion determined rightly upon a turning movement. All his previous attacks had either been frontal or had been made so by the enemy. His plan was to move eastwards with the IInd Division under Clery, while the Vth Division under Hildyard, who succeeded Warren when the latter was called away to Bechuanaland, advanced up the railway against the Boer centre. The IVth Division under Lyttelton, composed of the infantry which had been in Ladysmith during the siege, was kept in reserve pending the development of the turning movement, which began on May 11, and was skilfully conducted by Buller and was entirely successful. Places and rivers which had not been named in the chronicle of the war since October of the previous year now emerged from their obscurity. Elandslaagte became the fulcrum of an aggressive operation. Sunday's River and the Waschbank River after an interval of seven months were again crossed by British troops, not, like Yule's force, in hasty retreat, but in confident advance.

The Boers prepared for, and fully expected, a direct advance on Beith by way of Van Tender's Pass, but Buller made for the extreme flank of the range near Helpmakaar, which they held but lightly. It was rendered untenable on May 13, and after dark they retired on Beith, setting fire to the veld to mask the movement and hinder pursuit. At dawn Dundonald pushed on through the flames and smoke with his mounted infantry, but was checked by a body of Irish traitors who were acting as rearguard to their flying employers, and was unable to come up with the burghers. On the following night his patrols reported that Dundee was clear, and Buller occupied the town and reached Newcastle on May 18. The success of the turning movement was due in a great measure to a small force under Bethune, which had been lying for some months lower down the Tugela, and which Buller called up to threaten Helpmakaar from the south while he advanced from the west. It had been originally detached to protect his right flank during the advance on Ladysmith, and after long inaction as a watching force was restored to the strenuous campaign.

Of the rest of Buller's troops, one portion only, namely Hildyard's Division, was actively engaged in the movement. Its menace to the Boer centre near Glencoe, through which passed the railway to the north, attracted commandos away from the enemy's left flank at Helpmakaar and facilitated the turning movement. Lyttelton's Division and two cavalry brigades, which although Buller had informed Lord Roberts that he "was short of his proper strength" for the advance he had left behind near Ladysmith, took no part in it; and the absence of the cavalry allowed the enemy to retreat without molestation. The advance of Hildyard's Division was retarded, not by opposition, but by the duty which fell upon it of repairing the railway along which it advanced, and it did not reach Newcastle until May 27. On the 23rd Lytteltonand most of the cavalry were ordered up from Ladysmith.

As soon as Buller reached Newcastle he sent on Dundonald to reconnoitre the Laing's Nek position. On the west it was flanked by Majuba Hill, on the east by Pougwana, and was found to be strongly held. He therefore decided to make no further advance until he had concentrated his force at Newcastle. The cutting edge of the reconstructed Natal wedge had not as yet sufficient substance behind it to warrant its being put into operation. Pending the assembly of the Army Buller prodded across the Buffalo at Vryheid and Utrecht in order to safeguard his right flank. The expedition against the former town was ambushed and compelled to retire; while the two strong columns which were sent against Utrecht were hardly more successful. The town did indeed profess to surrender, but no garrison was left to enforce the submission, and on the withdrawal of the troops the Boers hovering in the hills returned like birds who have been temporarily scared out of their nests.

By the end of May, Buller's Army was concentrated in the northern corner of Natal. Towering over his left front was the Drakensberg Range through which Botha's Pass runs into the Orange Free State; on his right front was the Buffalo River with a difficult country beyond; and on his front was Majuba of ill-omened memory and Laing's Nek, over which the road to Volksrust and the Transvaal passed.

Buller remained at Newcastle for eighteen days, of which three were an armistice during negotiations for surrender with C. Botha, who was unable to accept the terms offered. On June 5 the advance was resumed, Laing's Nek being the immediate objective. At first Buller proposed to attack it directly, but soon after reaching Newcastle he found that the enemy was unassailably established on the position, and that it must be turned either from the east or from the west. The former movement would involve a wider detour through difficult country to the line of advance which would be taken up after the Transvaal was entered, and the western movement through Botha's Pass was therefore selected. Lord Roberts had for some time been in favour of it, but he had intended that it should be more than a mere turning operation. His advance from Bloemfontein had driven many of the commandos into the N.E. corner of the Free State, and he asked Buller to cross the Drakensberg and take them in rear by passing into the Transvaal by way of Vrede; but Buller could not be persuaded to remove himself so far from the railway. He had already missed an opportunity of co-operating with the main advance by a westward movement from Ladysmith to Van Reenen's Pass along the railway to Harrismith, where the presence of a division of the Natal Army would have been of the greatest use. The relations between Lord Roberts and Buller during the Natal campaign were rather those of leaders commanding the armies of allied nations than of superior officer and subordinate.