The Directorate of Military Intelligence (DMI) was a department of the British War Office.^[1]

Over its lifetime the Directorate underwent a number of organisational changes, absorbing and shedding sections over time.

The first instance of an organisation which would later become the DMI was the Department of Topography & Statistics, formed by Major Thomas Best Jervis, late of the Bombay Engineer Corps, in 1854 in the early stages of the Crimean War.^[2]

In 1873 the Intelligence Branch was created within the Quartermaster General's Department with an initial staff of seven officers.^[3] Initially the Intelligence Branch was solely concerned with collecting intelligence, but under the leadership of Henry Brackenbury, a protege of influential Adjutant-General Lord Wolseley, it was increasingly concerned with planning. However despite these steps towards a nascent general staff, the Intelligence Branch remained a purely advisory body, something that sharply limited its influence. The Branch was transferred to the Adjutant General's Department in 1888 and Brackenbury's title was changed to Director of Military Intelligence.

After Wolseley's appointment as Commander-in-Chief of the Forces in 1895, he made the Director of Military Intelligence directly responsible to him. At the outbreak of the Second Boer War in 1899 the Intelligence Branch had 13 officers. Prior to the war it produced a highly accurate summary of the Boer republics' military potential and was the only part of the War Office to escape criticism in the resulting Royal Commission. In the immediate aftermath of the Boer War the Intelligence Branch was enlarged and its head elevated to Director General of Mobilisation and Military Intelligence.

Following the Esher Report in 1904 the War Office was dramatically reorganized. The post of Commander-in-Chief was abolished and replaced by the Chief of the General Staff. Planning and intelligence would be the responsibility of the Directorate of Military Operations.

When the War Office was subsumed into the Ministry of Defence (MoD) in 1964, the DMI was absorbed into the Defence Intelligence Staff.^[4]

During World War I, British secret services were divided into numbered sections named Military Intelligence, department number x, abbreviated to MIx, such as MI1 for information management. The branch, department, section, and sub-section numbers varied through the life of the department; examples include:

Two MI section-names remain in common use, MI5 and MI6, in most part due to their use in spy fiction and the news media.

"MI5" is used as the short form name of the Security Service, and is included in the agency's logo and web address. MI6 is included as an alias on the Secret Intelligence Service website, though the official abbreviation, SIS, is predominant.

While the names remain, the agencies are now responsible to different departments of state, MI5 to the Home Office, and MI6 the Foreign Office.

Directors of Military Intelligence have been:^[9]

Deputy Quartermaster General, Intelligence Branch

• 1873–1878 Patrick Leonard MacDougall
• 1878–1882 Archibald Alison
• 1882–1886 Aylmer Cameron (Assistant Quartermaster General, Intelligence Branch)
• 1886–1888 Henry Brackenbury

Director of Military Intelligence

• 1888–1891 Henry Brackenbury
• 1891–1896 Edward Francis Chapman
• 1896–1901 John Charles Ardagh

Director General of Mobilisation and Military Intelligence

• 1901–1904 William Nicholson

Director of Military Operations

• 1904–1906 James Grierson
• 1906–1910 Spencer Ewart
• 1910–1914 Henry Wilson
• 1914–1915 Charles Callwell

Director of Military Intelligence

• 1915–1916 Charles Callwell
• 1916–1918 George Mark Watson Macdonogh
• 1918–1922 William Thwaites

Director of Military Operations and Intelligence

• 1922–1923 William Thwaites
• 1923–1926 John Burnett-Stuart
• 1926–1931 Ronald Charles
• 1931–1934 William Henry Bartholomew
• 1934–1936 John Greer Dill
• 1936–1938 Robert Hadden Haining
• 1938–1939 Henry Royds Pownall

Director of Military Intelligence

• 1939–1940 Frederick Beaumont-Nesbitt
• 1940–1944 Francis Henry Norman Davidson
• 1944–1945 John Sinclair
• 1945–1946 Freddie de Guingand
• 1946–1948 Gerald Templer
• 1948–1949 Douglas Packard
• 1949–1953 Arthur Shortt
• 1953–1956 Valentine Boucher
• 1956–1959 Cedric Rhys Price
• 1959–1962 Richard Eyre Lloyd
• 1962–1965 Marshall St John Oswald