[2][3][4] He was promoted to captain in November 1906[5] and then became adjutant at the Mounted Infantry School at Longmoor in 1908.
[2] He became General Officer Commanding 50th (Northumbrian) Division on the Western Front in April 1918 during the First World War.
[9] In 1919, Jackson married Dorothy Nina Seymour (1882–1953), one of five children of General Lord William Frederick Ernest Seymour and his wife, Lady Eva (née Eva Anna Caroline Douglas-Pennant).
Dorothy Seymour served with the Voluntary Aid Detachment and British Red Cross Society during the First World War.
She gained the rank of junior commander between 1939 and 1942 in the Auxiliary Territorial Service.