Yet the disaster was not due to his default alone, although the contributory defaults of others were rightly not permitted to excuse him. He had good reason to think that a well-mounted force would be able to take care of itself, and to believe that proper staff arrangements had been made for Spragge's march; but in each of these warrantable assumptions he was wrong. Lindley was the first of a series of disasters which seemed to show that Lord Roberts had pushed on too hastily.
Rundle's endeavour to help Spragge by a demonstration in the direction of Bethlehem soon came to an end. It is said that a telegram in which he announced the movement to Brabant fell into the hands of the Boers, who promptly utilized the information. On May 29 he was seriously checked at the Biddulphsberg, where they had taken up a position. He failed in an attack on what he believed was the Boers' flank but which was in reality their front. During the engagement he received a telegram from Head Quarters, dated three days previously, ordering him to join Brabant in the Ficksburg district, and he withdrew from the action, having suffered 186 casualties, some of which were caused by a fire which broke out in the long grass through which he had advanced, and in which helpless wounded men were lying. A brigade of Tucker's Division under Clements took his place at Senekal.
De Wet now set himself in person to execute the task entrusted to him by Botha of getting behind the British force in the Transvaal and breaking or interrupting the line of communication in the Free State. He had not long to wait for opportunities. He left Frankfort with 800 men, and on June 2 placed himself in observation near Heilbron, where Colvile was awaiting a supply column from the railway at Roodeval. The convoy was harassed from the first by mischances. Against Colvile's orders it was despatched with but a small escort and without guns. When he heard that sufficient protection could not be given, he counter-ordered the convoy, but the message did not arrive until after it had started.
On the second day of the march a body of the enemy was found blocking the road at Zwavel Kranz between Heilbron and Heilbron Road Station. It was De Wet waiting for the convoy.
The news of its plight reached Heilbron Road Station,[45] and a relieving column was sent out, which came within four miles of Zwavel Kranz. No firing, however, was heard, and the officer in command, hastily concluding that all was well, returned to the railway without finding the convoy, which next morning surrendered, the victim of easy-going indifference and neglect.
So far De Wet had done well, but he was only beginning his work. The railway between Bloemfontein and Vereeniging was weakly held by regiments of militia threaded like beads on a string in posts along the line. At Roodeval supplies and stores in large quantities, urgently needed by the Army in the Transvaal, were waiting until the bridge over the Rhenoster River, which had been destroyed by the Boers retreating before Lord Roberts, could be rebuilt. There was scarcely a post that did not beckon to De Wet to come to it.
He was within reach of the railway at three vulnerable points, and he divided the force to attack them simultaneously; himself taking command of the raid on Roodeval, which was held by casual details of departmental troops stiffened by a detachment of militia. Thus an important link in the chain was unable to bear a comparatively slight tension. No one was recognized as being definitely responsible for the railway north of Bloemfontein. The charge of it had been given to an officer who, unknown to the staff, was at the time in hospital and unable to take over his command; detachments were moved promiscuously by orders which came now from Pretoria and now from Bloemfontein; and in the chaos De Wet wriggled in between Colvile and Methuen.
On June 7 Heilbron Road Station, Rhenoster River Bridge, and Roodeval were captured in succession. At the Bridge the Derbyshire Militia fought gallantly for several hours, but were overpowered in a hopeless position, and soon afterwards Roodeval and its accumulated booty fell into the hands of De Wet,[46] who on that day severed Bloemfontein from Pretoria for a week and added nearly 500 men to the muster-roll of his prisoners of war.
It was evident to Lord Roberts that things had taken a serious turn, and that his position in the Transvaal was unsound. In framing his plans for the advance from Bloemfontein, he had naturally expected that the Natal railway would be available as an alternative line of communication soon after he entered the Transvaal; but the movements of Buller were deliberate, and nearly a third of it was still in the enemy's hands. It is probable that Lord Roberts would have been less disinclined to the "steam-rollering" policy if he could have foreseen that on the day he entered Pretoria the Natal Army would be still south of Laing's Nek.