Maxwell, Sir John Grenfell (1859–1929), soldier, was born 12 July 1859 at Aigburth, Liverpool, second son of Robert Maxwell, merchant, and his wife, Maria Emma Maxwell, daughter of Vice-Admiral John Pascoe Grenfell. He was educated at Cheltenham College and the Royal Military College, Sandhurst (1878–9), and commissioned into the 42nd foot (later the Black Watch) in 1879. Nicknamed ‘Conky’ because of his large nose, Maxwell spent most of his military career in Egypt. He served during the 1882 Egyptian war, and in the Gordon relief expedition of 1884–5. He was on the staff of his cousin General Sir Francis Grenfell and of Grenfell's successor as sirdar (commander) of the Egyptian army, Sir Herbert (later Earl) Kitchener (qv). In the late 1890s he commanded troops during the reconquest of the Sudan. In February 1900 he was appointed to command a brigade during the Boer war (1899–1902), with which he took part in the capture of Pretoria; he was subsequently military governor of Pretoria and in charge of the notorious camps, set up by Lord Kitchener (C-in-C, South Africa), where Afrikaner civilians were concentrated. He was knighted in 1900. In 1902 he became chief staff officer to the duke of Connaught and served him while he was successively C-in-C in Ireland (1902–4), inspector-general of the forces (1904–7), and C-in-C in Malta (1907–8). Maxwell was promoted major-general in 1906, and from 1908 to 1912 commanded the British troops in Egypt, after which, having no military appointment, he went on half-pay. In 1892 he married Louise Semina, daughter of Charles William Bonynge, a wealthy Irish-American. They had one daughter.
At the start of the first world war Maxwell briefly headed the British military mission at the French headquarters, but in September 1914 he resumed command of the troops in Egypt, where he successfully organised defences against a Turkish attack in February 1915 and presided over the huge expansion of his command as Egypt became a major British imperial military base, both for the ill-fated Gallipoli campaign (1915–16) and for operations in Palestine. In March 1916, having been superseded as general officer commanding in Egypt by Sir Archibald Murray, he was recalled home and was seeking further employment when the Easter rising broke out the following month. On Easter Thursday, 27 April, he was appointed C-in-C in Ireland. He was not the first choice of Lord Kitchener (now secretary for war), who favoured Sir Ian Hamilton, also available following the evacuation of Gallipoli, where he had been in command. But the prime minister, Asquith, anxious not to offend Irish sensibilities, objected: Hamilton had come under Irish nationalist criticism for the bungled landings at Suvla Bay on Gallipoli in August 1915, during which the 10th (Irish) division had suffered heavy casualties.
Equipped with sweeping martial law powers, Maxwell's task was to crush the rebellion and restore order. Taking into account the scale of the rising, its wartime context, and the widely held assumption that it had been fomented by the Germans, Maxwell's initially stringent security policy is scarcely surprising. He had little to do with the actual ending of the fighting, as the defeat of the rebels was inevitable by the time he arrived to take command in Dublin. But he was primarily responsible for government policy in the immediate aftermath of the rising. In a series of courts martial 171 prisoners were tried and 90 death sentences were imposed, of which Maxwell confirmed fifteen, which were carried out over a ten-day period. More than 300 other Volunteers, detained at the end of the hostilities, were immediately transported to camps in Britain. They were joined shortly afterwards by 1,800 men from among some 3,500 men and women (most of whom had taken no active part) arrested immediately after the rising, a procedure which clearly radicalised many of those involved. By imposing these draconian measures, Maxwell has been credited with powerfully accelerating the shift in Irish nationalist feeling away from Redmondite constitutionalism towards the militant separatism of Sinn Féin.
It is difficult to see what else Maxwell (or any other military governor of Ireland at the time) could have done. Although, seen with hindsight, his actions undoubtedly exacerbated the political situation in Ireland, his limited conception of how law and order had to be restored reflected both the inchoate nature of British policy-making generally towards Ireland, and the overriding imperative of maintaining domestic order while the United Kingdom was engaged in the titanic struggle of the first world war. That Maxwell, a middle-ranking general of no great reputation, was selected to go to Dublin reflects, moreover, how comparatively low down Ireland was in the scale of British political priorities in 1916. Maxwell himself was not unaware of the political consequences of wartime decision-making and, for example, opposed the introduction of conscription in Ireland, but he took much of the blame for the changing Irish political landscape and was effectively dismissed in November 1916. He was posted to the comparative backwater of the British domestic northern command, where he remained until the end of the war. After serving on Lord Milner's mission to inquire into the future government of Egypt (1919–20), he was not re-employed in the army and retired in 1922. Plagued by ill health in his later years, on his doctors' advice Maxwell went to South Africa, where he died (at Newlands, Cape Province) on 21 February 1929. There is a collection of Maxwell papers preserved at Princeton University Library.