In the third and final phase, beginning in March 1900 and lasting a further two years, the Boers conducted a hard-fought guerrilla war, attacking British troop columns, telegraph sites, railways, and storage depots. To deny supplies to the Boer guerrillas, the British, now under the leadership of Lord Kitchener, adopted a scorched earth policy. They cleared whole areas, destroying Boer farms and moving the civilians into concentration camps.
Battle of Poplar Grove. was an incident on 7 March 1900 during the Second Boer War in South Africa. It followed on from the Relief of Kimberley as the British Army moved to take the Boer capital of Bloemfontein. The Boers were demoralized following the surrender of Piet Cronjé at the Battle of Paardeberg.
After a succession of defeats, the Boers realized that against such overwhelming numbers of troops, they had little chance of defeating the British and so became demoralized. Roberts then advanced into the Orange Free State from the west, putting the Boers to flight at the Battle of Poplar Grove and capturing Bloemfontein, the capital, unopposed on 13 March with the Boer defenders escaping and scattering. Meanwhile, he detached a small force to relieve Baden-Powell.
On 15 March 1900, Lord Roberts proclaimed an amnesty for all burghers, except leaders, who took an oath of neutrality and returned quietly to their homes. It is estimated that between 12,000 and 14,000 burghers took this oath between March and June 1900.
British observers believed the war to be all but over after the capture of the two capital cities. However, the Boers had earlier met at the temporary new capital of the Orange Free State, Kroonstad, and planned a guerrilla campaign to hit the British supply and communication lines. The first engagement of this new form of warfare was at Sanna's Post on 31 March where 1,500 Boers under the command of Christiaan de Wet attacked Bloemfontein's waterworks about 37 kilometres (23 mi) east of the city, and ambushed a heavily escorted convoy, which caused 155 British casualties and the capture of seven guns, 117 wagons, and 428 British troops.