Montgomery’s military career began as a second lieutenant in the Royal Warwickshire Regiment in 1908; he was promoted Lieutenant in 1910, and Captain in 1914. He served as a Brigade Major in France from 1915 to 1917, as a General Staff Officer, Grade 2 (Temporary Major) from 1917 to 1918, and as a General Staff Officer, Grade 1 (Temporary Lieutenant Colonel) from 1918 to 1919. During 1919, he served with the British Army of the Rhine for several months, as a General Staff Officer, Grade 2. He returned to the role of Brigade Major with the 17th Infantry Brigade in Cork, from 5 January 1921 to 23 May 1922. Montgomery left Ireland to serve in the United Kingdom, in the Southern and later the Northern Commands. He served at the Staff College, Camberley, from 1926 to 1929, as a Deputy Assistant Adjutant General, and was an Instructor at the Indian Army Staff College at Quetta from 1934 to 1937. Montgomery returned to England as a Brigade Commander with Southern Command. In 1938, he was appointed a Major General, and given command of a division in Palestine and Transjordan.
