[5] After resigning his commission in March 1884,[6] Congreve, after graduating from the Royal Military College, Sandhurst, was re-commissioned as a lieutenant in the Rifle Brigade (The Prince Consort's Own) in February 1885[7] and promoted to captain in December 1893.

He was present at the Second Battle of Colenso when British troops commanded by Sir Redvers Buller attempted to cross the Tugela River to relieve the besieged city of Ladysmith.

Some of the horses and drivers were sheltering in a donga (gully) about 500 yards behind the guns and the intervening space was swept with shell and rifle fire.

Captain Congreve, with two other officers (Frederick Roberts and Harry Norton Schofield), and Corporal George Nurse retrieved two of the guns.

[9]Wounded, Congreve did not take part in the actual relief of Ladysmith in February 1900, but he was back in service later that year, and served as a staff officer.

He served as adjutant in a newly established colonial mounted infantry regiment which, with the leave of Lord Roberts, was named after his chief of staff, "Kitchener's Horse".

Lord Kitchener took over the chief command of British forces in South Africa in November 1900, and appointed Congreve his personal secretary.

[10] Following the end of hostilities in early June 1902, he left Cape Town on board the SS Orotava together with Lord Kitchener,[11] and arrived at Southampton the next month.

[16] In this post he excelled, and apparently, "greatly improved rifle skills, raising the rate of fire to fifteen armed shots a minute".

[14] At the outbreak of the First World War in the summer of 1914, Congreve was a temporary brigadier-general, having been promoted to that rank in December 1911,[17] when he assumed command of the 18th Brigade, part of the 6th Division.

[25] In order to "straighten the line,"[26] General Sir Douglas Haig, commander-in-chief (C-in-C) of the BEF, had decided to exploit the advances which had been made by Congreve in the south by taking and holding the town of Longueval and Delville Wood.

Being on fairly high ground and providing good spotting opportunities for artillery fire, an occupied Longueval would protect the right flank and allow the Allies to advance in the north and align their left with that of Congreve's XIII Corps on the right.

His service in the First World War is recorded, with that of his son William, in a Roll of Honour book in St Michael's Church at West Felton.