Daniel Theron became a Boer Army Captain and was put in charge of organizing and leading the Boer Intelligence scouts, the Theron se Verkenningskorps (TVK) (Theron’s Reconnaissance Corps). To save horses for combat, he developed the use of bicycles for despatch and reconnaissance. His 105 recruits were equipped with various items including revolvers, binoculars and sometimes light carbine. The TVK would watch British movements and study their tactics during battles. Reconnaissance missions became Theron’s specialty. He was able to move through the land without being detected. As the war progressed, Theron and his men were moved closer to the Western front. The Boers, under the rule of Piet Cronje, were constantly skimishing with British forces, and the TVK gained a reputation for destroying railway bridges. Lord Roberts labelled Theron “the chief thorn in the side of the British.”. A bounty was put on his head for £1,000 offered for his capture. Daniel Theron’s most notable single action was in the Battle of Paardeberg, where on 25 February 1900, a Boer Gen. Piet Cronje and several thousand troops were surrounded by British forces. Outnumbered and losing the battle, Theron, acting as a messenger for the other primary Boer commander, sneaked through British lines to convey a plan for a breakout operation – and then sneaked through the lines a second time to bring back Cronje’s reply. The TVK brought many Boer civilians and soldiers across the river safely into Boer territory, but in spite of Theron’s efforts the planned operation failed and most of the Boer forces surrendered.

After the British occupied parts of the Orange Free State in March 1900, Theron and the TVK became well known for the guerrilla campaign they conducted against the British Army. The TVK attacked trails and rail yards, ambushed and captured British soldiers and officers, blew up bridges, and freed captured Boer fighters from British prisons. On two separate occasions while scouting in the veldt in no-man’s land, Theron came upon the British Army Chief of Scouts, the American Frederick Russell Burnham. Both times the two men exchanged fire, but only at a distance. In July 1900, the British dispatched a unit of 4,000 soldiers to find and eliminate the TVK. After one skirmish with this force on 19 July, Theron managed to evade his pursuers and continue raiding, but the TVK was always on the run. While scouting alone on a koppie at Gatsrand, about 6 kilometres (3.7 mi) north of present-day Fochville, Daniel Theron encountered seven members of Marshall’s Horse and was killed in action.