Dutch rule ended, however, when in 1795, Britain seized Cape Colony during the French Revolutionary Wars, and at the general European peace of 1815, the colony became a permanent British imperial possession. From the 1830s, many Boers ventured north to establish independent communities that would later become the republics of the Transvaal and the Orange Free State, both of which shared borders with the British possessions of Cape Colony and Natal.
The source of the wars principally lay with the desire for British expansion into Boer lands, not least after the discovery of gold and diamonds. After the Transvaal was proclaimed in December 1880, conflict arose in what subsequently became known as the Transvaal Revolt or First Anglo-Boer War. Two thousand Boers invaded Natal and defeated a British force of 1,400 under General George Colley at Laing's Nek on January 28, 1881. The decisive encounter took place at Majuba Hill on February 27, when Colley, occupying a hill in the Drakensberg Mountains with a contingent of 550 men, lost 20 percent of his force, himself numbering among the dead. The British government had no desire to pursue the conflict further and on April 5, 1881 concluded the Treaty of Pretoria, which granted independence to the Transvaal, of which Paul Kruger became president. The discovery of gold in the Witwatersrand in 1886 increased British interest in the area and led directly to the annexation of Zululand, part of a strategy to isolate the Transvaal from access to the sea.
Internally, both Boer republics welcomed foreigners (known as Uitlanders) seeking work in the goldfields, but in the diamond industry and in various urban services, the Boers often resented what they perceived as a growing trend of immorality and licentiousness that permeated their strict, largely rural, Calvinist society. On the other hand, immigrants, most of whom came from Britain, resented the disproportionate share of taxation that fell on their shoulders and campaigned for a share in the political life of the country. Both Boer republics made large purchases of foreign weapons in 1899, and when Cape authorities refused to conform to an ultimatum from Pretoria to withdraw troops from the borders, hostilities opened in October, with the Boers assuming the offensive. On October 13, General Piet Cronjé laid siege to Mafeking, where Colonel Robert Baden-Powell, the future founder of the Boy Scout movement, made superb use of limited resources to establish a determined and successful defense. At the same time, forces from the Orange Free State invested Kimberley on October 15, while the main Boer blow fell on General Sir George White at Talana Hill and Nicholson's Nek later that month, forcing White's troops to take refuge in Ladysmith. In an effort to relieve the three towns, General Sir Redvers Buller divided his forces, a strategy that led to failure in all cases.
At the Modder River on November 28, General Lord Methuen, commanding a column of 10,000 men, seeking to relieve Kimberley, found his progress blocked by 7,000 Boers under Cronjé and Jacobus de la Rey. After losing almost 500 killed and wounded, Methuen succeeded in driving through the Boer lines, but his exhausted troops required rest, and no pursuit was possible. The British army was slow to appreciate three fundamental lessons: first, it was nearly impossible to inflict anything beyond negligible losses on Boer defenders occupying entrenched positions; second, smokeless, repeating rifles, fired from concealed positions, rendered frontal attacks costly, nearly supportable affairs; and third, since all Boer forces were mounted-even if, through force of numbers, they were eventually driven off-they could simply vanish into the veldt, reform, and fight again on another occasion. The British army could not, at least initially, offer an adequate answer to such tactics, for it possessed paltry numbers of mounted forces, and was obliged to rely heavily on Cape yeomanry units. Until the arrival of mounted reinforcements, therefore, British troops were forced to cover vast areas of enemy territory on foot, with little or no opportunity of pursuit even when success on the battlefield invited it.
Despite growing numbers of reinforcements, the British continued to find themselves bested by opponents both more determined than themselves and with considerable more knowledge of the ground. At Stormberg, on December 10, a British force under General Sir William Gatacre lost heavily in an ambush; the same day, at Magersfontein, 8,000 Boers under Cronjé entrenched themselves on a hill overlooking the Modder River and inflicted heavy casualties on Methuen's force, which not only unwisely attacked frontally in heavy rain, but without extending into open order. The third British disaster of what became known as Black Week took place at Colenso on December 15, when 21,000 men under Buller, seeking to relieve Ladysmith, crossed the Tugela River and attempted to turn the flank of General Louis Botha, in command of 6,000 Orange Free State troops. The Boers, dug in as usual, easily drove off their adversaries, whose flank attack became encumbered by broken ground. Buller suffered about 150 killed and 800 wounded, together with more than 200 men and 11 guns captured.
