Throughout the month of May there had been alarms and excursions in the capital of the South African Republic. The sound of the plon-plon of the British Army was daily growing more distinct. The house of Ucalegon was on fire. The Volksraad met on May 7, and after a session of three days handed over the situation to the wavering executive Government, which had already made arrangements for an eastward retirement. Kruger, fearing lest his retreat by the Delagoa Bay railway should be cut off, slipped away to Machadodorp on May 29; the forts were emptied and abandoned, and Botha was bidden to do the best he could with the remnants of the Transvaal forces. On June 3 he took up a position on a ridge a few miles south of the city and prepared for the worst.
French, on the left front of the advance, was ambushed in a defile by a commando which had come up out of the west, but cleared himself with slight loss. The forts were dumb. Only the ridges between the city and Six-Mile Spruit were found to be held. The southern ridge was taken, and when the northern ridge was turned by Ian Hamilton, who was recalled from acting at large in support of French, the Boers retired. French passed through Zilikat's Nek and marched on Pretoria north of the Magaliesberg. On June 5 the capital of the South African Republic surrendered to Lord Roberts.
The Boers streamed away towards the east. An attempt made a few days before to cut the Delagoa Bay railway failed, not, however, through the fault of Hunter-Weston, who led the enterprise. The force given to him was insufficient for the purpose, and he was unable to repeat the exploits of Bloemfontein and Kroonstad.
The prisoners of war, whom to the number of 3,000 the Boers had not been able to drag away with them in their hurried flight, and who were in confinement at Waterval twelve miles north of the city, were brilliantly liberated on June 4 by some squadrons of cavalry; which not only ran the gauntlet of the Wonderboom defile, but passed through the Boer posts at the further Poort and snatched away the prize from under the eyes of Delarey, who was covering Waterval with 2,000 burghers and some guns.
On the day of Lord Robert's entry into Pretoria, Buller was still in Natal. They had started simultaneously, and in thirty-four days the main body had marched 300 miles, but the tardigrade Natal Army was now on Lord Roberts' right rear. It had been his hope that Buller would advance step by step with him, and having reached the Transvaal, would strike northwards and establish himself on the Delagoa Bay railway and deny it to Kruger. At Kroonstad, Lord Roberts, seeing that he could not expect assistance from Buller, contemplated detaching Ian Hamilton and sending him into the Eastern Transvaal, but the fear of unduly weakening the main body in view of probable opposition at the Vaal, Johannesburg, and Pretoria, caused him to give up the project. As events turned out, it would in all probability have been successful.
Pretoria was in the hands of the British Army, Kruger was in flight, the war was over said the experts. Without having fought a single action that could be termed a battle, and at a cost of less than 500 casualties, of which but sixty-one men were killed, Lord Roberts had passed from Bloemfontein and had seized the perverse city in which most of the South African troubles of the past twenty-five years had been brewed. The Free State, though kicking, was apparently helpless. There were, however, not a few observers on the spot to whom the easy success and the few casualties were of ominous import. A change in the method of the opposition to be offered in the future to the invader was indicated. The Boers were discovering that they were incapable of waging systematic warfare and were on the point of resorting to guerilla, for which they, as well as the arena, were by nature particularly well adapted.
On the Boer side there was a transitory interval of weakness. Even before Lord Roberts' occupation of Pretoria Kruger wrote doubtfully to Steyn; and after it Botha was inclined to negotiate with the invader. He was with his commandos at Hatherley, a few miles east of Pretoria. A Council of War was held in the office of a Russian Jew, who was a distiller of whisky. The leaders complained that they had been deserted by Kruger, who had slunk away with the civil government and all the money he could lay his hands on, and the general opinion was in favour of abandoning the struggle. A meeting between Lord Roberts and Botha was even arranged, when suddenly De Wet intervened. The news of his successful raids on the line of communication in the Free State relaxed the tension of the minds of the despondent commandants. Easily disheartened and easily reassured, they leapt in an instant from one psychological pole to the other. Botha announced that he was ready to meet Lord Roberts, not only in conference, but in battle. The negotiations were, however, not definitely broken off until after the Battle of Diamond Hill.
Lord Roberts had sent Kitchener with a column to see to the trouble in the Free State, and could not put more than about 16,000 men into the field against Botha, who, with 6,000 men, had taken up a strong position astride the Delagoa Bay railway sixteen miles east of Pretoria. His centre was at Pienaar's Poort, where the railway passes through a defile, and his front, which his former experience of Lord Roberts' tactics led him to extend greatly, was nearly twenty-five miles in length, and ran along an irregular chain of hills, kopjes, and ridges. Facing the Diamond Hill and Donkerhoek range, south of the centre, is another range of heights through which the two poorts Tyger and Zwavel pass, and which circles round the source of Pienaar's River towards the Diamond Hill range. North of the centre runs a broken range ending abruptly at the Kameelfontein ridge, which overlooks the broad Kameelfontein valley leading to the Krokodil Spruit; and across the valley rises the Boekenhoutskloof ridge, a detached feature with triangular contours, which, being somewhat in advance, commands the approaches to Kameelfontein ridge, where the Boer right flank under Delarey was posted.