Yzer Spruit and Tweebosch introduced the Drive into the Western Transvaal. Troops from all quarters reinforced Kekewich at Klerksdorp, and soon a force 14,000 strong was assembled there and elsewhere. The difficulty of the task before it was enhanced by the absence of a network of blockhouse lines, which had only been laid out along the Schoon Spruit and thence to Lichtenburg and Mafeking, and also along the Vaal. The troops had to begin operations from a faulty strategical base, as they were aligned along or near the Schoon Spruit blockhouse line, and between the Boers and that line. To drive Delarey on to it, they must rapidly place themselves west of him; and this could be done only by a night march of mounted men darting through his commandos and then pressing him on to the Schoon Spruit in the opposite direction. The operation, which was of spirited and ingenious conception, was carried out on March 23. In proportion to the effort--the force engaged in it numbered 11,000 mounted men--the results were paltry. A few score prisoners and three guns were taken. As in the earlier drives in the Orange River Colony, the meshes of the net were spacious and fragile. Delarey, Kemp, and Steyn escaped; and even Liebenberg, when about to suffer the _peine forte et dure_ upon the Schoon Spruit blockhouse line, found a discontinuity through which he wriggled at midnight. Delarey mustered his burghers to the number of over 2,000 on the Hart's River. To deal with the embarrassing situation the British columns were again marched to the west, with instructions to form a line of three entrenched camps distant one or two days' march from the Schoon Spruit. The centre column under the command of W. Kitchener having reached its destination, made a reconnaissance in force still further to the west on March 31. Cookson, who was in charge of the expedition, at the end of a march of thirty-five miles, during which he had pushed back small parties of the enemy, halted at Boschbult, where two farms lay on the banks of the Brak River. Cookson soon found himself in presence of 2,500 Boers with four field guns, his own strength being 1,800 with the same number of guns. The position was a bad one as the ground rose on each side of the river; the bush offered cover to the attack, and the only cover available to the defence was the almost dry bed of the river. He threw out screens and proceeded to entrench and form a laager; while the screens faced in the open the fire of the enemy under cover in the bush on the high ground. Liebenberg made one attempt from the south to charge the main position, but was driven back by the southern screen which had been brought into the river bank; and after a second unsuccessful attempt, this time from the east, withdrew to the high ground on the north.