Meanwhile there was energy on the left. Methuen had been for some time in occupation of the Boshof district, where he was in a position to threaten Kroonstad as well as the commandos at the Vaal bridge at Fourteen Streams between Kimberley and Mafeking. The relief of the latter was to be undertaken by a flying column under Mahon supported by Hunter's division. On May 3 Lord Roberts left Bloemfontein for the north. Kelly-Kenny's Division remained in charge of the Free State capital, while Chermside's policed the railway and the country in rear. Rundle at Thabanchu was instructed to prevent the enemy from regaining a footing in the districts east and south of Bloemfontein, and Methuen to push on towards the left bank of the Vaal beyond Hoopstad. No definite orders were sent to Buller, but for two months there had been a constant interchange of suggestions, counter-suggestions, plans, and projects for co-ordinate action.
Lord Roberts' objective was now Pretoria. The country in front of him was not difficult and he had a railway behind him. The line of communication with the south was fairly safe, and it was estimated that not more than 12,000 Boers with twenty-eight guns, under Delarey and L. Botha, who had been brought round from Natal to take chief command during the crisis, barred the way into the Transvaal; not including the loosely associated commandos operating on the right flank under the general control of De Wet, the Prince Rupert of the Boer War.
The nearest Boer post was at Brandfort, a few miles north of Karee Siding. On the right was the Winburg intervening column, 14,000 strong, under Ian Hamilton, who dragged in his train a weak supporting Division under Colvile, his superior officer in an anomalous position obliged to conform to his movements, and without authority to direct them. Brandfort was occupied that evening by Lord Roberts at the cost of six men killed. Vet River, the next obstacle, was secured on May 5, and crossed on the following day by the greater part of the main column. Ian Hamilton went into bivouac eight miles north of Winburg, which was occupied by his henchman Colvile.
Up to this time, Lord Roberts was acting without the cavalry under French, who since the Sannah's Post affair had been working in the Thabanchu district, and who joined the main column on May 9. Though his horses were not in good condition, his arrival increased the power of the centre to strike rapidly at the next obstacles, the Zand River and the town of Kroonstad forty miles beyond, which was now the seat of the Free State Government. The drifts on a section of the river nearly twenty miles in length were seized, the most easterly being taken by Ian Hamilton, who had gradually converged on the centre column and was now on the right of the line. Next day the passage of the river was effected; but Lord Roberts' hope of getting round and grappling each flank of the enemy, who numbered about 3,000 Transvaalers and 5,000 Free Staters, was not realized, and Botha withdrew without serious loss. That night the Army went into bivouac astride the railway between Zand River and Kroonstad.
On the left was the cavalry under French, who next morning raided northwards; but although he was unable, owing to the opposition of a force which came out of Kroonstad, to reach the railway north of the town, a small party of pioneers whom he had sent on succeeded during the night in blowing up the line at America Siding within a few yards of the high-road by which the enemy was retreating. This daring exploit, which although it had not much effect on the situation was not the less meritorious, was carried out by Hunter-Weston, who, just two months previously, had similarly cut the line north of Bloemfontein. The Boers had taken up a position at Boschrand to defend Kroonstad on the south, but French's turning movement scared them, and the position as well as the town was abandoned, in spite of efforts made by Steyn and Botha to arrest the flight. The seat of Government was transferred to Lindley.
The Zand River affair was an incident in the advance rather than a battle. Lord Roberts suffered but 115 casualties. Its effect on the enemy was chiefly moral. The Transvaalers, whose country had not yet heard the sounds of war, were alarmed, but the Free Staters were dismayed. The ties of race and kindred had engulfed them in a war which was not for their own cause, and the brunt of which they had borne for ten weeks. They thought that they had done all that could be expected of them and that the Transvaal must now look after itself. From that time there was no organized co-operation between the allies.
On May 12 Lord Roberts entered Kroonstad. In his advance, averaging thirteen miles per day, he had outstripped the reconstruction of the railway, of which almost every bridge and culvert had been blown up by the retreating Boers, and many miles of the permanent way had been destroyed. A halt was therefore necessary until the railhead could be brought nearer, and to give the Army an opportunity of pulling itself together, which was especially required by the cavalry. Little more than one-half of the 6,000 horses with which French marched out of Bloemfontein on May 6 were fit for service at Kroonstad seven days later.
Ian Hamilton was sent out in chase of the flitting Free State Government. He found it not at Lindley, nor at Heilbron, for it had trekked away to Frankfort. Between Lindley and Heilbron he was attacked in rear by a body of Boers, who emerged from the presumed vacuum behind him, but they were beaten off.
The bulk of the enemy's force which had evacuated Kroonstad, was now in the triangle formed by the railway, the Vaal and the Rhenoster. On its left flank was Ian Hamilton; and French was ordered out to hook the right flank, a repetition of the movement which had failed at Zand River. On May 22 Lord Roberts left Kroonstad.