[3][5] From 3 November 1915[6] until 16 August 1916[7] he served as aide-de-camp to Lieutenant-General Richard Haking, then in command of the 11th Army Corps, finally returning to his regiment on 16 September 1916.

[3] From February 1919 he served as the adjutant of a Dispersal Unit[11] (overseeing the demobilization of conscripts[12]), until on 29 May 1919 he was appointed a Staff Captain[13] in the 2nd Guards Brigade.

[3] On 1 February 1936 he was appointed military attaché in Paris (as a General Staff Officer, 1st Grade, or GSO1, on half-pay)[24] with the brevet rank of colonel.

[27] On 29 August 1938 Beaumont-Nesbitt was appointed the Deputy Director of Military Intelligence at the War Office, and granted the temporary rank of brigadier.

[28] On the day following the declaration of war, 4 September 1939, he was made an acting major-general,[29] and took over as Director of Military Intelligence after the former incumbent Henry Pownall was appointed Chief of Staff of the British Expeditionary Force.

[31] On 15 January 1941 Beaumont-Nesbitt was re-granted the temporary rank of major general,[32] to serve as a military attaché, and from 15 June 1941[33] as a member of the British Army Staff, in Washington DC.