In addition to their service records, medals documents and possible mentions in operational records as discussed elsewhere on this site, there are two additional and most valuable sources of information about commissioned officers.

The Army List

Each month, the War Office published a complete listing of all officers in the Army List. The list is organised by regiment, with officers shown in order of seniority. That means that they are split by rank, going from the highest (Field Marshal) down to the lowest (Second Lieutenant). All men at a given rank are listed in ascending order of the date at which they were promoted. Each volume has an index, so if you do not know the man's regiment you should be able to track him down. An officer's career can be recreated to a large extent from consulting the Army List.

A full set is available at the library at the National Archives, but copies of the lists exist at many other libraries and resource centres.

The London Gazette

All officer's promotions and appointments were printed in the London Gazette.

Most were reproduced a few days later by the Times newspaper. An online, searchable version of this exists as the Times Digital Archive. This is not a free internet resource, but it is accessible from universities (via the Athens system) and at many libraries in the UK. The archive is occasionally free to use at the Times website.