Born in 1854, the second son of General Sir William Codrington, he was educated at Harrow and entered the Coldstream Guards in 1873. He first saw active service during the Anglo-Egyptian War of 1882, where he was mentioned in despatches. He later commanded the 1st Battalion Coldstream Guards in the Second Boer War between 1899 and 1902, where he was wounded twice. He took part in the Battle of Magersfontein on 10–11 December 1899, in which the defending Boer force defeated the advancing British forces amongst heavy casualties for the latter. Codrington was mentioned in the despatch from Lord Methuen describing the battle and how he "though wounded, insisted on remaining in command of his battalion till nightfall". He was again wounded and mentioned in despatches later in the war, and given a brevet promotion as colonel. For his service, he received the Queen's medal with three clasps, and the King's medal with two clasps. After his return to the United Kingdom, he was placed on half-pay as he resigned his command of the 1st battalion on 28 October 1902. He commanded the 1st London Division of the Territorial Force from 1908 to 1909, when he was appointed Major-General commanding the Brigade of Guards and General Officer Commanding London District, retiring from this post in 1913. He returned to duty after the outbreak of the First World War, serving as the Military Secretary to Lord Kitchener, the Secretary of State for War, from August until October 1914. He was then appointed to command Third Army in the Home Forces; this was based around Luton, and contained four Territorial divisions and two Territorial cavalry brigades. He relinquished command in 1916. He was appointed to sit on a Pensions Appeal Tribunalin the summer of 1917, which dealt with appeals against governmental decisions on military pensions, and later published a book on War Pensions: Past and Present, co-authored with Edward Abbott Parry, another member of the Tribunal. His final military position was the ceremonial colonelcy of the Coldstream Guards, to which he was appointed in 1918. Unusually, this had been a position previously occupied by his father. He was appointed chairman of the Society of Miniature Rifle Clubs in 1917, and President of the Association in 1932.