The agile mind of Lord Roberts rather than the heavy hand of his Chief of the Staff is discernible in the method of the advance on the Transvaal.
There were two courses open to the British Army. It might have deliberately pulverized and extinguished each atom of opposition within reach in the Free State, and have taken no step to the front until the rear and the flanks were absolutely and finally clear of the enemy; or it might have advanced boldly towards the Transvaal with the ordinary precautions for the protection of the lines of communication and of the flanks.
Lord Roberts adopted the latter course. He had tried it with success in the Afghan War twenty years before, when he marched even more "in the air" from Kabul to Kandahar. The tedious process of "steam-rollering" the Free State was not to his taste, nor would the expectant British public at home have understood it; and it would have been severely criticized by the military experts. It would have concentrated before him north of the Vaal all the Boer forces which could not be crushed on the spot, and have left the resources of the Transvaal for some time untouched: free communication with the outer world by way of the neutral port of Lorenzo Marques, the treasury of the Johannesburg gold mines upon which the enemy could draw, and the railway and mining workshops in which munitions of war could be manufactured.
Lord Roberts therefore determined upon a swift advance from Bloemfontein. He was confident that the occupation of places would bring the war to an end without an excessive loss of life; and he would probably have been right if he had been engaged in a European war. He did not see, however, that the Boers derived little or no strength from their towns, which were rather a source of weakness; they were men of the veld and the veld was their strength.
De Wet's guerilla advanced Chermside to the command of the IIIrd Division, in place of Gatacre sent home. A new Division, numbered the VIIIth, under a new commander, Sir Leslie Rundle, a general with an Egyptian reputation, was assembled south of Bloemfontein in April.
The siege of Wepener called for activity from Bloemfontein as well as from the Orange, and Lord Roberts sent Rundle to Dewetsdorp, where his presence would, it was hoped, not only draw the Boers away from Wepener, but deny them a retreat to the north. Pole-Carew with the XIth Division and French followed Rundle, but De Wet abandoned the siege on the approach of Hart and Brabant from the south, and his brother P. De Wet scuttled away from Dewetsdorp on the approach of Rundle; and the commandos ran the gauntlet successfully. Their hereditary trekking instincts told them when to move and how to move, and their mobility had not at that period been recognized by the British Staff. Wepener was indeed relieved, though not from Bloemfontein, but the subsequent divagations of the Boers baffled three British divisions which were endeavouring to squeeze them northwards and head them off. A strong rearguard was left by the Boers at Houtnek, ten miles north of Thabanchu.
Lord Roberts' position at Bloemfontein, and on the line of communication, had never been seriously endangered. The brilliant affairs of Sannah's Post and Mostert's Hoek were no doubt annoying to the British Army and encouraging to the enemy. At home the importance of them was greatly exaggerated. If the advance on the Transvaal was delayed by them and the subsequent operations arising out of the siege of Wepener, more time was given to prepare for it; and the British Army was usefully informed of a fact which hitherto had hardly been suspected, namely, that the enemy derived much of his power from mobility, resourcefulness, and aptitude for guerilla.
Lord Roberts' plan for the movement on the Transvaal was an advance in line, on a front which extended from Ladysmith to Kimberley. It soon became an echelon owing to the slow movements of Buller in Natal. In the centre at Bloemfontein were the troops under the immediate orders of the Commander-in-Chief; on the left at Kimberley were Methuen, and Hunter with the Xth Division which had been brought round from Ladysmith. Between the centre and the right the intervention of Basutoland and the Drakensberg prevented the effective co-operation of the Natal Army with Lord Roberts; and a portion of the interval was occupied by the enemy.
The centre columns under Lord Roberts were about 43,000 strong. Hunter and Methuen in the west had each under his command about 10,000 troops, while Buller's force, which was much nearer to the Transvaal objective than the centre, and which was still lingering on the banks of the Klip River two months after the relief of Ladysmith, numbered about 45,000. Ian Hamilton, who had done so well in the Elandslaagte and Caesar's Camp affairs, was not allowed to waste himself in the Natal lethargy. He was recalled from Ladysmith, and after taking part from the Bloemfontein side in the Wepener operations, was given command of a column which was sent on, a few days before the general movement, in the direction of Winburg to protect the right flank of the central advance and to fend off from it the hovering Boer commandos which had been pressed northwards by the April operations. He started from Thabanchu on April 30 and was soon in action with the Boer force a Houtnek under P. Botha. The battle lasted until nightfall and was renewed next day, when, with the help of reinforcements from French and Colvile, Ian Hamilton forced the Boers to retire on Clocolan.