The Boer War (aka Second Anglo-Boer War, South Africa War, and Second War of Freedom, 1899 to 1902) was won by the British but only after it employed controversial policies such as scorched-earth tactics and civilian concentration camps, both intended to deprive the Boers of logistical support. A watershed conflict, the Boer War involved technologically advanced weaponry, was followed closely by the British public thanks to newsreels and photography, and was one of the first major wars where civilian deaths far outweighed those of combatants.

The British and Boers had long been rivals in Southern Africa, competing for land and resources between themselves and African kingdoms throughout the 19th century. The Boers were settlers in Southern Africa with Dutch ancestry (and that of certain other European countries, notably Germany and France). The name Boer means "farmer." They were also known as Afrikaners because they spoke Afrikaans. They had first arrived in the 17th century, and they eventually created two republics: Transvaal (1852) and Orange Free State (1854). These republics were created after the Great Trek of the 1830s, a Boer migration away from British control in the south. The Boers had not agreed with the British policy of abolishing slavery and resented the increasing influence of Anglo-Saxon culture on their own. Meanwhile, British settlers created the colonies of Cape Colony (1806) and Natal (1843), principally to safeguard the Cape of Good Hope, an important stopping point on shipping routes between Europe and Asia. Both the British and the Boers had acquired their land at the expense of African states.

The British claimed a nominal suzerainty over the Boer republics, one which the Boers rejected. The regional rivalry heated up considerably following the discovery of diamonds in Griqualand in 1867. The British made Griqualand a crown colony in 1871 and merged it with Cape Colony in 1873. The blatant British takeover of the diamond mines at Kimberley was bitterly resented by the Boers. Then gold was discovered in 1886 in Witwatersrand in Transvaal. The British, who heavily invested in the mines, were equally bitter that these new riches were controlled by the Boers.

The Boer republics continued to expand, but a loss to the Pedi gave the British the excuse to annex Transvaal in January 1877, claiming that only a British military presence would guarantee security. This led to the First Anglo-Boer War (1880 to 81), really a series of skirmishes, which the Boers won. The peace conventions that followed contained ambiguous wording regarding British suzerainty over the Boer republics.

The British were also expanding their borders and had defeated the Zulu Kingdom in the Anglo-Zulu War of 1879. Zululand became a crown colony in 1887 and was absorbed into Natal in 1897. British expansion continued with the establishment of the Basutoland Protectorate (modern Lesotho, 1884), British Bechuanaland and the Bechuanaland Protectorate (modern Botswana, 1885), and Swaziland (1893). The acquisition of these territories backfired spectacularly, since the Boers were released from fighting Africans and could now concentrate on their fight for territorial expansion against the British.

Anglo-Boer relations sank to new depths with the Jameson Raid at the end of 1885. Unhappy at the Boer control of the Rand mines and the discriminatory laws against British residents in Transvaal, a group of mine owners attempted a coup. The raid failed completely, and the British authorities disowned it. The president of Transvaal, Paul Kruger (1825 to 1904), responded by buying weapons from Germany and France and forming a military alliance with the Orange Free State. This, in turn, convinced British colonial authorities that a Boer-German alliance could seriously threaten British dominance in Southern Africa and scupper the ambition to create a single British-controlled colony, the Union of South Africa. Kruger's discrimination against non-Boer White residents, called Uitlanders ('Outsiders') by the Boers, gave what the British considered a moral justification for war. With the British mobilising reserve troops, Kruger issued a 48-hour ultimatum to the British government on 9 October 1899, demanding that British troops be withdrawn from Transvaal's borders. The British refused to comply, and war was declared on 11 October.

The Boers knew they had to act quickly before the British government in London sent additional troops. The Boer fighters were not professionally trained troops, but they were well-equipped with the latest rifles, machine guns, and artillery pieces. Perhaps the biggest asset of the Boers was their knowledge and use of local terrain. Organised into commandos, the Boer fighters were highly mobile. Such was their skill at shooting long-range smokeless rifles and blending into the veld that "The Boers were largely an unseen force, and confronting them with traditional volley-fire or hand-to-hand fighting proved difficult, if not impossible" (Fremont-Barnes, 7). Boer marksmanship meant British officers abandoned their traditional swords for revolvers and removed conspicuous badges of their rank to avoid being shot first.

Other innovations in this conflict that bridged the gap between traditional 19th-century infantry warfare and 20th-century mechanized warfare included the use of the telegraph, combined artillery and infantry attacks, the extensive use of volunteer soldiers on both sides, blanket coverage in the daily press, the use of cinematic film to record events, and the publication of personalised records made by soldiers in the form of diaries and photographs. It was also one of the first conflicts to witness a massive patriotic souvenir industry develop, where soldiers and generals were emblazoned on everything from boxes of matches to porcelain mugs.

The Boers enjoyed several early successes, notably in the middle of December 1899, during what the British called 'Black Week.' The Boers won the battles of Stormberg, Magersfontein, and Colenso. Then another famous Boer victory came at the Battle of Spion Kop in January 1900. All in all, the British commanders were guilty of too many blunders and of underestimating the enemy. Unrealistic objectives, like taking well-defended hills, issuing confusing orders, poor communication systems, and inadequate maps, all played their part in these defeats. The Boers proved that, although not professionals, they would not be the pushovers the British generals and public had hoped they would be.

The Boer leadership did make the mistake of tying down a significant number of their fighters in sieges such as at Ladysmith, Kimberley, and Mafeking. Here were British garrisons, and the idea was to tie them down and take them out of the war, but, in reality, the Boers themselves needed to commit a large number of fighters to keep the sieges going. The siege of Mafeking (1899 to 1900) became symbolic of the war, first of all by indicating that this was no ordinary colonial war against a technologically inferior enemy. Indeed, the conflict was much more like a European civil war in terms of weapons used. Secondly, this siege and others showed that civilians would be heavily involved and become frequent casualties. The besieged British garrison and allied Tswana warriors held out for 217 days, and its resourceful commander, Robert Baden-Powell (1857 to 1941), became a national hero. The town of Mafeking was saved by a relief column in May 1900. This siege and others proved the error of the Boer strategy: they could not win a war of attrition against the much more powerful British Empire.

Unlike in the First Boer War, the British government was willing to send colonial troops to Africa. The British force, which included 30,000 colonial troops from Australia, New Zealand, and Canada, in this way soon rocketed from 25,000 to 250,000 men. The Boers could field no more than 60,000 men. This numerical advantage helped the British to control the railway lines and defeat a Boer army at Paradeberg in March 1900. The major Boer town of Bloemfontein was seized next. On 24 May, the Orange Free State was taken over by the British and renamed the Orange River Colony. A week later, Johannesburg was captured. In June, Pretoria was taken by the British, and in October, Transvaal was annexed.

In response to the increasing number of military reversals, the Boers adopted guerrilla tactics, attacking and quickly withdrawing from skirmishes and also making raids into Cape Colony. Unable to defeat the enemy in one large engagement, the British responded with an effective but controversial scorched-earth tactic, where crops were destroyed and livestock confiscated. Thousands of civilian farms and homes were burned to the ground during the campaign. The British commander-in-chief, Herbert Kitchener (1850 to 1916), restricted the Boers' movement by dividing "both the ex-republics into a huge steel chequerboard made of barbed wire fence lines, guarded by concrete blockhouses" (Pakenham, 577).

Kitchener also had thousands of civilians interred in concentration camps to prevent them from supplying the Boer fighters in the field. Other civilians were detained simply because their homes had been destroyed during the conflict. Kitchener's strategy was effective but drew widespread outrage both at home and abroad. The wilful negligence of the detainees and woefully inadequate planning for medical and food supplies resulted in up to 28,000 Boer (80% of whom were children) and 20,000 Black African deaths due to malnutrition and disease. By way of comparison, 7,000 Boers were killed as combatants during the war, and 22,000 on the British-led side.

Following the public outrage and questions in parliament, the first step toward improving conditions in the camps was to take control away from the army and put the civilian authorities in charge. Kitchener ended the scorched-earth policy in December 1901 and ordered that no more Boer women and children be arrested. Around 117,000 Boer women and children and 119,000 Black Africans had been detained in 46 concentration camps.

The last major battle of the war was won by the British at Roodewal on 11 April. The Second Boer War came to an end on 31 May 1902 with the Treaty of Vereeniging. Boer prisoners of war were released in June and July. Besides the thousands of human casualties, material losses were great in the war, too. Over 30,000 homesteads had been burned down, and millions of livestock killed. At least one-third of a million horses were killed in the conflict.

It was an expensive victory, the war having cost Britain £200 million (equivalent to 21,000 million today). More and more voices in Britain, among which was that of the economist and social scientist J. A. Hobson (1858 to 1940), began to question the point of imperialist foreign policy both from an economic and a moral perspective. The public, perhaps for the first time, was exposed to theories by Hobson and others that suggested powerful private actors with vast wealth were deciding the fates of nations, and doing so at the taxpayers' expense and for no benefit other than their own business interests.

As part of the peace negotiations, the rights of Black Africans (whose leaders were not invited to the peace talks) were left in the air until White self-government was achieved. Over 100,000 Black Africans had helped the British war effort as soldiers, scouts, runners, grooms, porters, servants, and labourers. They had hoped for change, but the only result was that Black Africans continued to suffer from discriminatory laws; indeed, their situation actually worsened in this respect, and they were effectively excluded from political voting. In 1910, both former Boer republics, along with Cape Colony and Natal, as well as several former African kingdoms, were unified into a single colony: the Union of South Africa, whose government was dominated by the Afrikaners.