In a disastrous week, dubbed Black Week, from 10–17 December 1899, the British Army suffered three devastating defeats by the Boer Republics at the battles of Stormberg (690), Magersfontein (948) and Colenso (1,138), with 2,776 men killed, wounded and captured. The events were an eye opener for the government and troops, who had thought that the war could be won very easily.
British units were armed with then-modern magazine-fed small arms, the .303 caliber Lee Enfield and Lee Metford, and breech-loading field artillery. Boers were armed with the 7mm 1893 Mauser rifle, and fielded German-built breech-loading field artillery. The British, however, were accustomed to fighting tribal wars with tactics more suited to the Napoleonic era, and had no tactical doctrine in place to fight against a foe also armed with the same modern weapons, and suffered accordingly.
With new, modernized troops came new tactics; only a few months after Black Week, one of the main cavalry divisions led a flanking march that ended with a victory. Besides equipping the cavalry with rapid-firing rifles instead of lances, the new British military doctrine also started using artillery as a defensive unit of the army, and saw innovation in the use of machine guns.
These new volunteers served as a "new face, untainted by defeat and accusations of defeatism…to breathe life back into the campaigns and restore hope at home." Other changes enacted by the British immediately following the Black Week disaster were the mobilization of two more divisions, the calling up of the army reserves, raising a force of mounted cavalry for better mobility, and most importantly by sending volunteers from home overseas which added more than one hundred thousand additional troops by the end of the war.
During Black week, the War Office took primacy, as the Colonial secretary took a back seat in the cabinet, the Boer War raged on. Chamberlain was eclipsed in Cabinet during December 1899. It must have been a blessing in disguise for the man himself: had he accepted Salisbury's initial offer he would have been at the War Office dealing with the difficulties in the Cape. The Liberal Unionist was not going to be a scapegoat for Conservative policy. The reverses and humiliations for the Army hit the London government hard.
Arthur Balfour was acting Prime Minister, and Lord Lansdowne, Secretary for War. Lord Salisbury, grieving at Hatfield for his dead wife, was incapacitated. Cometh the hour, and Chamberlain was hailed as a great statesman, raised to the occasion by the debility of Lord Salisbury, the titan of foreign policy. Chamberlain wanted a tolerant liberal civilized Empire, and a generous reconstruction of South Africa.
Lord Methuen was on the march to Kimberley, only 25 miles away. Unscreened from the Boer's trenches in the town, the mounted force lost 500 men. But they managed to wheel round to cross the Modder River by nightfall. There he rested from 1 to 7 December using the river for refreshments. They fully expected Redvers Buller to simultaneously march on Ladysmith in north Natal. These blows they hoped would end the war by Christmas. By Lord Milner's assessment conveyed to London, 70,000 troops would be needed to complete the business. Milner's concern over losses mitigating success on the field had caused a rethink of the situation in the Transvaal.
...If we had known all we do now, I suppose that we should have taken up a position probably at Colenso and left all the northern part of Natal undefended. We ought also probably to have abandoned Mafeking.
One serious deficiency was the low velocity artillery which shot less far than the Boers excellent guns.
On Monday 11 December, General Gatacre's night attack into strong Boer defences at Stormberg had ended in failure. The enemy had modern rifles, accurate artillery, bandoliers for all, and proven horse commandos. Gatacre lost two guns, and 700 men, of whom 500 were prisoners. The senior officers had left them behind. But as usual the Boers did not bother to pursue.
On the Modder, Methuen's division of 15,000 frontline troops ran into heavily dug-in Boers on the Magersfontein Heights. The British artillery barrage warned the Boer of the impending assault, led by the Highland Brigade in the monsoon rains in the darkness. At dawn they were caught by a murderous cross-fire. Major-General Wauchope became a high-ranking casualty. The British casualties were 1000 men to the Boers' 250. The defeat delayed the relief of Kimberley.
In Natal, Buller was already pessimistic about the coming battle, although in England they only knew his great reputation. On Friday, December 15, he tried to cross the river. A sortie from Ladysmith might have taken the Boer pickets on Hlangwane Hill, but its significance was overlooked. The British lost 1100 men killed, ten artillery guns lost. A humiliating retreat was ordered at nightfall although half the army had not yet engaged the enemy. Lord Roberts' son was killed. Buller, at his wits end, advised Ladysmith to surrender, but Sir George White pledged to fight on.
Liberal leader Henry Campbell-Bannerman declared from Aberdeen on December 19,
"The gravity of the situation, the formidable character of the campaign as now disclosed ...these furnish no ground for doubt or for despondency.... We have a united people in this country, and in every part of the Empire, and with these forces on our side moral and material success is certain.... Mr Chamberlain is largely responsible for this war.
Consequences of the defeats
The British government drastically changed their mindset after the Black Week disaster to the realization that the Boer war would not be an easy victory or won by Christmas. They undertook many changes in the military including military personnel, better mobilization, and better modernization in order to match and then surpass the Boer troops. Many different opinions arose in the United Kingdom. Although there were many doubters who criticized the overall justice of the British cause, the patriots who would end up volunteering, fighting, and winning this conflict were the majority. Following Black Week, the government called "for able-bodied men willing to abandon their homes and families and risk their lives to serve their country." Even with this dangerous task, many still volunteered either for the regular army or for shorter enlistments.
Buller's decisions at Ladysmith caused him to be sacked and replaced with Lord Roberts. It was the end of a career for the man the press dubbed "Sir Reverse" Buller.
Another consequence was the recruitment within months of 30,863 new troops from Canada, Australia and New Zealand. These were ordered by the Imperial Conference held in 1902. 8400 Canadians volunteered, of which 600 Horse were raised by Lord Strathcona in British Columbia.
Of the Australians, 6208 came from New South Wales, 3897 from Victoria, 2903 from Queensland, 1494 from South Australia, 1165 from Western Australia, 796 from Tasmania. About 6000 from New Zealand. The Canadians were eager horsemen, and when the matter was settled on the day after Colenso, the necessity of cavalry doctrine was acknowledged. Since Black Week large numbers of Australians were encamped awaiting departure. The day after Buller's defeat Premier of New Zealand Richard Seddon telegrammed Chamberlain declaring how they would be delighted to help.