5920594 Blockhouse, South Africa, 1901 circa (b/w photo) by Unknown photographer, (20th century); National Army Museum, London; (add.info.: ?Blockhouse?, 1901 circa. Photograph by Second Lieutenant O T R Crawshay, 6th Battalion, The Warwickshire Regiment, Boer War (1899-1902), 1901 circa Each blockhouse was surrounded by a stone wall about 0.6m high. Circular and radiating trenches were dug between forts and stone sangars erected, allowing the garrison to get outside and fight from prepared defensive positions if the Boers attacked. Barbed wire entanglements completed the defences. From a collection of photographs taken by Second Lieutenant O T R Crawshay, 6th Battalion Warwickshire Regiment, 1900-1914.); by National Army Museum .