Britain's military involvement in Afghanistan is a contentious subject, yet it is often forgotten that the current conflict is in fact the fourth in a string of such wars dating back more than 170 years. Aiming to protect British India from the expanding Russian empire, the British fought a series of conflicts on Afghan territory between 1838 and 1919. The Anglo-Afghan wars of the 19th and early 20th centuries were ill-conceived and led to some of...