He remained for some weeks seeing to the drifts, which were now in his possession and now in that of the enemy. A Boer raid into Rhodesia on November 2 forced the outlying detachments back upon Tuli, which was seriously threatened by some commandos under F.A. Grobler of Marico. The Government of Pretoria, however, growing anxious at the presence of British troops elsewhere, vetoed a promising enterprise and recalled him. The raid of November 2 was answered a few weeks later by Plumer, who, finding the drifts unoccupied, reconnoitred thirty miles towards the south. Nearly six months elapsed before another British soldier set foot in the Transvaal. A subsequent reconnaissance again found no trace of the enemy on the left bank of the Limpopo, and showed that it was unnecessary for him to remain on the river. He had the advantage of being cut off from communication with superior officers ignorant of local conditions, and was able to act freely upon his own responsibility.
He soon heard news which clearly indicated the way he should go. The railway from Buluwayo to Mafeking was held as far as possible towards the south by patrols of police under Nicholson, and the Rhodesian Volunteers under Holdsworth were also on the line. In the gap between the railhead and Mafeking, a Boer commando, said to have been detached from Mafeking by Cronje, was at Sekwani on the N.W. border of the Transvaal and within striking distance of the Western line. It was face to face with the border tribes and was soon in trouble with them. Although they were not allowed to attack Sekwani independently, they were permitted to co-operate as non-combatants in an attack which Holdsworth was about to make on it, but only on the condition that they did not cross the Transvaal border. This was a refinement of policy which they could hardly be expected to understand, and they precipitated Holdsworth's action by attacking the Boer laager, which lay but a mile or two across the border, on their own account, and the operation had therefore to be abandoned. To avenge this native attack, in which several burghers had been killed, reinforcements were brought over by the Boers from the Pietersburg line, and Holdsworth's position at Mochudi on the Western line, whither he had retired after the Sekwani failure, was endangered.
This was the news which reached Plumer at the end of the year. His original instructions were obsolescent and he readily adapted himself to the altered situation. He saw that it was more important to clear the railway north of Mafeking than to remain where he was on the chance of a Boer invasion of Rhodesia, of which his reconnaissances south of the Limpopo saw no sign. The nearest station on the Western line was Palapye, and on December 27 he set out on his midsummer march of 170 miles to it. Within a fortnight, his little force of irregulars, which three months before had been sent out into the South African wilderness to perform duties that might have engrossed a division, passed away from Tuli beyond the Limpopo on to the visible stage of war near Mochudi.
In the middle of January, 1900, he reached Gaberones. On his left flank Sekwani was still occupied by the enemy, though in reduced numbers; in front of him the Boers were not only strongly posted on the railway at Crocodile Pools, but able to draw upon Mafeking for reinforcements, by the help of which they successfully resisted an attack on February 11. Plumer's force, though augmented by detachments he had picked up on the line, was unequal to the task of advancing along it. He therefore decided to diverge from the railway and advance by way of Kanya, a native town lying twenty miles west of the line.
On March 6 he reached Lobatsi, where he was forty-five miles from Mafeking. He found, however, that it was an awkward place to defend and soon quitted it, as Baden-Powell seemed to be in no immediate need, and was in fact averse to Plumer's small force throwing itself upon the besiegers. With the greater part of his command, the rest being sent back to hold the railway at Crocodile Pools, he withdrew to the base which he had established at Kanya; afterwards advancing to Sefetili, thirty miles from Mafeking, where he awaited the approach of Mahon's relieving column from the south. Baden-Powell, rejoicing in his siege, was not anxious that the game which he was playing so well should be brought to a premature conclusion, and was more afraid for Plumer than for himself.
Plumer filled in his two months at Kanya and Sefetili by occasional raids in the direction of Mafeking and by an expedition towards Zeerust. The column in the south, of whose movements many false reports reached him from time to time, seemed to be tarrying by the way, and it was not until May 12 that he received a message from Lord Roberts that it was nearing its destination.
For some weeks after his entry into Bloemfontein, Lord Roberts was unable to arrange for the direct relief of Mafeking by a column specially detailed for the purpose. He had originally intended that this should be done by Methuen, but subsequently ordered him to operate in the Free State on the left flank of the advance on the Transvaal. He hoped to apply his favourite method of an automatic relief, brought about by external pressure elsewhere. At the end of April, however, when it had become an urgent matter, he ordered Hunter, who had recently arrived at Kimberley from Natal, to send out a mounted force under Mahon, following it himself with the rest of the Xth Division.
He left Kimberley on May 3, and on the following day Mahon set out from Barkly West on his 230 miles' march to Mafeking. Mahon advanced wide of the railway up the Hart's River, which joins the Vaal at Barkly West, his right flank being covered by Hunter, who kept close to the Vaal. Mahon met with no serious resistance until he had covered 200 miles of his journey, when he found a force which had been sent down from Mafeking across his path, and which diverted him to Massibi; where he joined Plumer on May 15.
The advance of the main and less mobile body under Hunter was aided by demonstrations made by Methuen from Boshof. With three columns claiming their attention the bewildered Boers were unable to do more than offer a stout but ineffectual resistance to Hunter on the Vaal on May 5. Two days later he occupied Fourteen Streams and restored the railway communication across the Vaal, having during his halt taken possession of Christiana, a village in the Transvaal a few miles up the river. It was now no longer necessary for him to hurry after Mahon, and his advance northwards was made at leisure. Early in June he occupied Lichtenburg, where Mahon rejoined him.
Mafeking as well as Kimberley were now in the hands of Lord Roberts, but the Western line joining them to Capetown was not yet secure. The districts of Cape Colony west of De Aar and Hopetown were remote and backward, and sparsely inhabited by discontented and unprosperous Dutch farmers. Nearly a year before, while the Cape Government was placidly blinking under the shadow of Table Mountain and only taking action that thwarted the attempts of the Imperial Government to prepare for war, and like the unjust steward intriguing for reception in Boer houses if the Empire should fail, arms had been sent into these districts by the Boers of the Republics, and courses of instruction in the use of them were actually being held.