After attending the Royal Military College, Sandhurst, Marindin was commissioned as a second lieutenant into the Black Watch (Royal Highlanders) on 7 November 1891,[1][2] and was promoted to lieutenant on 16 February 1896.[3]
He served in South Africa during the early part of the Second Boer War from 1899 to 1900, as a special service officer. First employed in Base Commandant′s Office, he was then on Transport duty, then served as Staff Officer (graded Staff Captain from 29 April 1900)[4] to Rest Camp, Bloemfontein, and subsequently to the Officer Commanding troops at Bloemfontein and Southern lines of communication. He was promoted to captain while in South Africa, on 21 October 1900.[5]
Following the end of the war and his return to the United Kingdom, Marindin was in January 1903 seconded from his regiment and appointed Instructor at Staff College, Camberley.[6][7]
He saw action during the First World War. He was appointed acting General Officer Commanding the 35th Division on a temporary basis on 27 March 1918: that division was involved in a series of fighting withdrawals since being committed to battle on 25 March 1918 near Cléry-sur-Somme, some 13 miles (21 km) east of Dernancourt. He was confirmed in that post on a substantive basis on 7 April 1918. Marindin went on to command 3rd Highland Brigade as part of British Army of the Rhine in March 1919.
He was appointed a Companion of the Distinguished Service Order in the 1918 New Year Honours[10] and a Companion of the Order of the Bath in the 1919 Birthday Honours.[11]
In January 1932 he was made honorary colonel of the 6th/7th Battalion, Black Watch, a Territorial unit.[12]