In 1968, Malcolm Yapp, future distinguished historian of the Middle East and author of Strategies of British India, wrote a series of articles describing in detail the British occupation of Afghanistan between 1839 and 1842. These articles are probably the most authoritative histories of the series of disturbances and rebellions that brought instability to Afghanistan during the first British occupation. This is strange when one considers that the articles are based almost exclusively on one source. This is not criticism; far from it. Known as the Enclosed Secret Letters, these documents comprise several thousand pieces of correspondence from British political officers stationed throughout Afghanistan. The usual health-warnings apply: there are forgeries and inaccuracies; they are all copies, hand-written in the political department at Calcutta, with all the attendant errors such a process causes. Treated carefully though, these documents provide the most complete record of British occupation forces in Afghanistan. The information in those letters also provides some of the most comprehensive analysis of the political, social and cultural characteristics of the various tribes of Afghanistan.