During Methuen's halt at Modder River Delarey and Cronje received considerable reinforcements. From Natal, from the Basuto border, and from Kimberley, commandos were summoned to Spytfontein. That position was, however, for the reason just stated, insecure; and on the December 4 the Magersfontein position was taken up and prepared for defence by Delarey. A low arc stretching from the position towards the Modder was discovered, from which a flanking fire could be poured in upon a frontal attack.
With an unerring instinct which was more useful to him than most of the knowledge he could have acquired in a European Staff College, and with an originality which if it had been displayed by a young British officer in an examination for promotion would probably have injured that officer's prospects, Delarey dug his trenches not at the foot of the hill but in sinuous lines some little way in advance of it, by which he gained the power of meeting an attack with grazing or skimming fire, and which also removed the firing line from physical features on which the British guns could be laid. It is said that he manned the works on the slope with burghers firing black powder so as to draw the enemy's fire away from the trenches in which only smokeless powder was used.
Methuen obtained little information during his halt at Modder River. The country was so much intersected by the wire fences of the farms that cavalry scouting was difficult. He decided to make a direct frontal attack upon Magersfontein on December 11 after a bombardment on the previous evening; and here, as at Colenso, the text-book preliminary shrapnel practice put the enemy on the alert and did no harm. It greatly encouraged the burghers in their trenches. Only three men were touched by the projectiles hurled by the naval, howitzer, field, and horse batteries; and an impending infantry advance was clearly indicated. To the Highland Brigade under Wauchope, who had joined the command since the Modder River battle, was entrusted the execution of the night attack. He does not appear to have altogether approved of Methuen's scheme; but with the same dogged valour which he displayed many years before when he threw himself upon the Gladstonian political Magersfontein in Midlothian, he incorporated himself in it.
At 1 a.m. on December 12 in a storm of rain and thunder the Brigade in mass of quarter-columns marched out of its bivouac, guided by a staff officer's compass which the lightning and the rain soon made unreliable. The objective point was the southern edge of the Magersfontein Ridge, about three miles distant. The progress made over the rough and encumbered veld was slow, and it was difficult to judge in the darkness how much ground had really been covered. Wauchope either underestimated the distance made good or, as is more probable, did not expect to find the enemy entrenched in advance of the foot of the hill, and the error cost him his life and the lives of many other gallant Highlanders. Afraid lest dawn should find his Brigade too far away from the position to rush it, he hesitated to deploy, and when at last he was about to give the order, a further delay was caused by a line of thorn bushes. The Brigade passed through or avoided the obstruction and was at the halt on the point of changing formation when the Boers in the advanced trenches, which had been so stealthily excavated that no one in the British Army seems to have been aware of their existence, received the alarm and opened fire. Possibly the situation might have been saved if an order to charge had been given at once, and the Highlanders had heard the skirl of the pipes; but Wauchope had at the first shot rushed forward impetuously towards the flashing Mausers. With his life he measured the unknown distance to the trenches, and at the supreme moment his Highlanders lost their leader and knew not whom to follow.
The sudden stroke of the impact falling upon men of dissimilar temperament reacted on them diversely. The majority absorbed it by throwing themselves upon the ground on which they stood; others recoiled mechanically upon the companies in rear; while to not a few it was a stimulus which projected them into the jaws of death gaping before them in the dim light. A mixed body, hardly exceeding the strength of three companies, pushed on in obedience to the last words that fell from Wauchope's lips, to reinforce the right; and succeeded in wriggling round the eastward flank of the enemy's advanced trenches and in shattering a foreign contingent in the Boer service which was holding the gap of level ground between the low arc and the Magersfontein Ridge. The little force of progressives came under the fire of the British guns which opened upon the ridge at daybreak, but a remnant under Wilson drove a keen-edged but slender wedge into the curve of the Boer position, and was favourably placed to storm the ridge. A few score of Highlanders were now fingering the key with which it seemed possible to unlock the sluice gates and allow the flood waters of war to overwhelm the foe. But War is a game of chance. The key was snatched away and the issue of the day reversed by a man who had lost his way.
In the absence of Delarey, who was absent at Kimberley, P. Cronje was in chief command of the Boer forces. His Head-Quarters were at Brown's Drift on the Modder, six miles from the key of the position on Magersfontein. The sound of the bombardment notified him that an infantry attack was imminent, and he hurried off to make the final arrangements for meeting it. These he seems to have completed to his satisfaction, and he rested for an hour or two, rising soon after midnight. In the darkness and rain he lost his way on the unfamiliar ground. But chance found him at daybreak close to the gap which Wilson's little band of Highlanders had hewn in his line, and their promising advance was effectually repressed, as they were simultaneously fired on by Cronje's escort on their front and by a commando which had come up on their right rear.
Daylight found the shattered and dismembered Highland Brigade lying in patches upon the veld, with their leader dead before their eyes; themselves unable to advance or retreat, conspicuous, hungry, thirsty, and soon to be scorched by the midsummer sun at the zenith; and there they lay for eight hours. Only the shells of the artillery, which from daylight onwards played upon the trenches and partially mastered the fire from them, saved the Highland Brigade from destruction.
The Guards' Brigade under Colvile was in the first instance detailed as the reserve of the Highland Brigade, but the repulse of the latter and the probability that it would sooner or later be compelled to retreat gave the former a definite objective, the low arc held by the left of the Boer line. In marching on this the wire fence which was the boundary between British territory and the Orange Free State was crossed, and the Guards' Brigade had the honour of being the first body of troops to go into action in the enemy's country. Colvile held his own, but although he was unable to occupy the arc he screened the right flank of the Highlanders. On their left a weak Brigade under Pole-Carew was drawn up astride the railway, and thus apparently the firing line, which had been so hardly pressed during so many weary hours, was secure on either flank. But Pole-Carew was paralysed by the variety of the duties which had been assigned to him, and was unable to operate offensively on the enemy's right. His original orders were to act as camp guard and to demonstrate northwards in support of the Highland Brigade; and subsequently he seems to have been instructed to hold himself in readiness to cross over to support the Guards' attack on the enemy's left, with the result that his Brigade was never seriously engaged.