John Adams was born at Combe Florey in the county of Somerset, England, on 26 September 1890. Prior to the First World War he migrated to Australia and worked as a valet. Military service was not new to Adams, as he had served with the Royal Navy for two-and-a-half years, and he enlisted with the Australian Imperial Force on 18 August 1914, a month before his 24th birthday. It was around this time that he also started documenting his experiences in his diary, a practice that he would continue until mid-1916. After two months of training he departed Sydney with the 2nd Infantry Battalion aboard HMAT Suffolk on 18 October 1914.

Adams and the 2nd Battalion were part of the second and third waves sent ashore at Gallipoli on 25 April 1915. He writes extensively about the landing in his diary, particularly about the confusion that pervaded the initial stages and his attempts to find members of his battalion during the subsequent days. Although Adams remained with his unit until the evacuation in December 1915, he was wounded on several occasions. During the battle of Lone Pine in August the glass of the periscope he was looking through was shattered and his eyesight was damaged. In September 1915 he was knocked unconscious by a loop-hole plate sent flying by shell-fire.

After being transferred to the newly formed 54th Infantry Battalion in February 1916, Adams served during its first major engagement on the Western Front, the disastrous battle of Fromelles. He was promoted to lieutenant on 2 August 1916, having risen quickly through the non-commissioned ranks. In April 1917 he was Mentioned in the Despatches of Field Marshal Sir Douglas Haig, Commander of the British Expeditionary Force, for his work as an intelligence officer with 14th Brigade headquarters and also for his actions at Fromelles. This was followed by the receipt of the Military Cross in June 1918 for his work as an intelligence officer during the winter campaign on the Somme and his subsequent conduct in Belgium during 1917 on return to his battalion. It was reported that his "fearlessness, gallantry and devotion to duty" left a good impression on those with whom he came into contact. Adams was later awarded a Bar to his Military Cross for "conspicuous gallantry and brilliant leadership during the operations at Peronne" in 1918, where he was wounded while rushing a machine-gun post.

After the war Adams left for Australia on 6 May 1919, though he would briefly return to England to be married. John Adams died at the age of 90 at Concord, New South Wales, on 21 June 1981.