John Gethin Hughes was born at Campbelltown (Bluff), New Zealand, on 13 March 1866. He was the son of Mary Agnes McLean and her husband, John Gethin Hughes, a mariner. John junior, who was known as Jackie, attended school in Akaroa and Timaru. He then became a law clerk, and between 1884 and 1887 served in C Battery, Timaru's volunteer artillery unit. Hughes moved in 1888 to Napier, where early in 1891 he enlisted in F Battery. He rose through the ranks, and in 1897 was elected battery commander. In 1898 he was made adjutant and captain of the 3rd Battalion Wellington (East Coast) Rifle Volunteers. A keen sportsman, Hughes represented Hawke's Bay in rugby and rowing and played cricket, polo, golf and tennis.
Following the outbreak of the South African War in October 1899, Jackie Hughes enlisted in the First New Zealand Contingent as a private. During a farewell speech to Napier volunteers, he stated that 'he would rather be a trooper fighting for his country than the richest landholder in Hawke's Bay'. The contingent arrived in South Africa in November. Hughes's considerable abilities were quickly recognised, and in late December 1899 he was commissioned in the field as a lieutenant. On 15 January 1900 he distinguished himself during a counter-attack against Boers who were trying to seize a hill (later known as New Zealand Hill) overlooking the British camp at Slingersfontein. For his gallantry during this hard-fought action Hughes became the first New Zealand serviceman to be appointed a DSO. He was one of the contingent's outstanding officers, and was mentioned in dispatches before his unit returned to New Zealand in January 1901.
Early the same year Jackie Hughes was appointed assistant staff officer to the commandant and was commissioned as a captain in the New Zealand Militia. During 1902 he briefly returned to South Africa as a captain in the Tenth Contingent. Prior to the First World War Hughes held various staff positions in the New Zealand forces. He felt, probably with some justification, that he was the victim of unfair treatment by Richard Seddon, the minister of defence; it was not until January 1907, after Seddon's death, that he was belatedly promoted to major.
Hughes married Marion (Maisie) De Vere O'Connor at Wellington on 8 May 1909; they were to have two sons and a daughter. In June 1909 Hughes and his wife travelled to Australia and then to England. Although Hughes undertook some training with the British Army, his visit had not been approved by the New Zealand authorities and caused some controversy. On his return in late 1910 he transferred to the newly established New Zealand Staff Corps.
In 1914 Hughes was appointed assistant military secretary to the commander of the New Zealand Expeditionary Force, Major General Sir Alexander Godley. Following the outbreak of the First World War he embarked for Egypt in September. On 7 June 1915 he was promoted to lieutenant colonel and given command of the Canterbury Battalion of the New Zealand Infantry Brigade, which he led during the Allied offensive at Gallipoli during August 1915. On 7 August the Canterbury Battalion took heavy casualties when Hughes unwittingly chose to reform his men in an area dominated by a newly emplaced Turkish battery. Early in October his health collapsed and he was admitted to hospital suffering from paratyphoid, iritis and dysentery. Eventually, in July 1916, he was invalided back to New Zealand. For his services at Gallipoli Hughes was mentioned in dispatches and made a CMG.
Due to the poor state of his health, Jackie Hughes was discharged from the New Zealand Expeditionary Force at the end of 1916. The following year he was posted to the retired list and granted the honorary rank of colonel. During his retirement Hughes was a leading figure in the First New Zealand Mounted Rifles Association. He died at his home in Wellington on 23 July 1954, survived by his wife and children.
Although his military career was handicapped by his limited military education, Jackie Hughes was a brave and conscientious officer who was highly regarded by Godley. At Gallipoli he generally seems to have performed competently under very difficult circumstances. He was a sociable, tactful man and a 'likeable chap'. As his commanding officer commented in 1914, he had 'a personality which draws him to all with whom he comes in contact'.