|Years of service||1901–1904|
|Commands held||10th Battalion King's Royal Rifle Corps|
182nd (2/1st Warwickshire) Brigade
9th (Scottish) Division
63rd (Royal Naval) Division
|Battles/wars||Second Boer War|
First World War
|Awards||Companion of the Order of the Bath|
Companion of the Order of St Michael and St George
Distinguished Service Order & Bar
Blacklock was a Militia officer when he was commissioned into the King's Royal Rifle Corps as a second lieutenant on 5 January 1901. He served in South Africa during the Second Boer War, and took part in operations in Orange River Colony. While in South Africa, he was promoted to lieutenant on 11 December 1901. Following the end of the war, he returned home on the SS Sicilia in October 1902. Blacklock resigned his commission on 23 April 1904, while his battalion was stationed in India, and emigrated to Canada, where he settled at Port Rowan, Ontario.
Following the outbreak of the First World War, Blacklock returned to England to rejoin his old regiment and quickly achieved promotion. He served as commanding officer of 10th Battalion of the King's Royal Rifle Corps from December 1915. He went on to be commander of the 182nd (2/1st Warwickshire) Brigade in 1916 and then commander of the 97th Brigade in 1917. He was wounded during the Battle of Guillemont in September 1916 and was awarded a Bar to his Distinguished Service Order for his actions. He was appointed General Officer Commanding 9th (Scottish) Division in March 1918 and General Officer Commanding 39th Division later that month. In this position he oversaw the 39th Division's robust defence of the Somme in the face of the German Spring Offensive. Following the Division's retirement from the front line, Blacklock was made General Officer Commanding 63rd (Royal Naval) Division in August 1918. His commanding officer, General Sir Charles Fergusson considered Blacklock to be the "finest commander he had ever seen." Blacklock also received the praise of other senior wartime leaders for his command style, including General Horne and Field Marshall Haig. Blacklock retired from the Army for a second time in 1920, by this stage a major general, and returned to Canada. He had been invested as a Companion of the Order of the Bath and a Companion of the Order of St Michael and St George in recognition of his military service.
- University of Birmingham Archived 27 September 2013 at WebCite
- "No. 27434". The London Gazette. 16 May 1902. p. 3253.
- "The Army in South Africa - Troops returning home". The Times (36881). London. 24 September 1902. p. 7.
- Liddell Hart Centre for Military Archives
- Simon Robbins, British Generalship During the Great War: The Military Career of Sir Henry Horne (1861–1929) (Ashgate Publishing, Ltd., 2010), 11.
- Army Commands Archived 5 July 2015 at the Wayback Machine
| General Officer Commanding the 9th (Scottish) Division
13–16 March 1918
C. E. Lawrie
| General Officer Commanding the 63rd (Royal Naval) Division
30 August 1918–1919