The volunteer companies of the infantry returned also to England, and so did nine militia battalions, whose place was taken however by an equal number of new-comers.
The British position was very much strengthened during the winter by the adoption of the block-house system. These were small square or hexagonal buildings, made of stone up to nine feet with corrugated iron above it. They were loopholed for musketry fire and held from six to thirty men. These little forts were dotted along the railways at points not more than 2000 yards apart, and when supplemented by a system of armoured trains they made it no easy matter for the Boers to tamper with or to cross the lines. So effective did these prove that their use was extended to the more dangerous portions of the country, and lines were pushed through the Magaliesberg district to form a chain of posts between Krugersdorp and Rustenburg. In the Orange River Colony and on the northern lines of the Cape Colony the same system was extensively applied. I will now attempt to describe the more important operations of the winter, beginning with the incursion of Plumer into the untrodden ground to the north.
At this period of the war the British forces had overrun, if they had not subdued, the whole of the Orange River Colony and every part of the Transvaal which is south of the Mafeking-Pretoria-Komati line. Through this great tract of country there was not a village and hardly a farmhouse which had not seen the invaders. But in the north there remained a vast district, two hundred miles long and three hundred broad, which had hardly been touched by the war. It is a wild country, scrub-covered, antelope-haunted plains rising into desolate hills, but there are many kloofs and valleys with rich water meadows and lush grazings, which formed natural granaries and depots for the enemy. Here the Boer government continued to exist, and here, screened by their mountains, they were able to organise the continuation of the struggle. It was evident that there could be no end to the war until these last centres of resistance had been broken up.
The British forces had advanced as far north as Rustenburg in the west, Pienaar in the centre, and Lydenburg in the east, but here they had halted, unwilling to go farther until their conquests had been made good behind them. A General might well pause before plunging his troops into that vast and rugged district, when an active foe and an exposed line of communication lay for many hundreds of miles to the south of them. But Lord Kitchener with characteristic patience waited for the right hour to come, and then with equally characteristic audacity played swiftly and boldly for his stake. De Wet, impotent for the moment, had been hunted back over the Orange River. French had harried the burghers in the South-east Transvaal, and the main force of the enemy was known to be on that side of the seat of war. The north was exposed, and with one long, straight lunge to the heart, Pietersburg might be transfixed.
There could only be one direction for the advance, and that must be along the Pretoria to Pietersburg railroad. This is the only line of rails which leads to the north, and as it was known to be in working order (the Boers were running a bi-weekly service from Pietersburg to Warm Baths), it was hoped that a swift advance might seize it before any extensive damage could be done. With this object a small but very mobile force rapidly assembled at the end of March at Pienaar River, which was the British rail-head forty miles north of Pretoria and a hundred and thirty from Pietersburg. This column consisted of the Bushveld Carbineers, the 4th Imperial Bushmen's Corps, and the 6th New Zealand contingent. With them were the 18th battery R.F.A., and three pom-poms. A detachment of the invaluable mounted Sappers rode with the force, and two infantry regiments, the 2nd Gordons and the Northamptons, were detached to garrison the more vulnerable places upon the line of advance.
Upon March 29th the untiring Plumer, called off from the chase of De Wet, was loosed upon this fresh line, and broke swiftly away to the north.