The Defence of Duffer's Drift is a short book by Major General Sir Ernest Dunlop Swinton, published in 1904 when Swinton was a Captain. It appeared in the British United Service Magazine under the pseudonym, Lieutenant N. Backsight Forethought, who is the narrator of the book. The book is an exploration of small unit tactics in a fictional encounter in the Boer War. Swinton served in South Africa during the Boer War, and the book "embodies some recollections of things actually done and undone in South Africa, 1899-1902."
Lieutenant Backsight Forethought ("BF") and his command of fifty men are given the task to defend Duffer's Drift, a natural ford to a river. A large force of Boers, unknown to BF, is moving toward his position. This scenario is played out six separate times, in six "dreams." In the early scenarios, BF and his British troops are ignominiously defeated. After each defeat, BF learns lessons and adapts his strategy for the later encounters. The later dreams end more inconclusively, and in the final dream, BF and his command successfully hold out long enough to be relieved. The book encourages critical thinking and careful use of position and terrain to mount a successful defence.
The Defence of Duffer's Drift was reprinted in the April 1905 edition of the Journal of the United States Infantry Association. The book, especially intended for young lieutenants, has become a military staple on small unit tactics, read far afield in places such as the United States, Russia, and Canada. While some of the advice has become rather dated - notably, BF eventually decides to imprison all nearby locals, shoot any livestock that could be of aid to the enemy, and impress both Boer and black alike into building fortifications for his men - the book is still considered relevant and interesting in modern times.