Tandy was a career army officer. He was a cadet at the Royal Military Academy, Woolwich and joined the Royal Artillery as a second lieutenant on 26 February 1898.[5]
He fought in the Second Boer War, leaving Southampton for South Africa on the SS Canada in early February 1900.[6] Promotion to lieutenant followed on 16 February 1901. He was mentioned in Sir Redvers Buller's report to Lord Roberts on the campaign: "2nd Lieutenant E. N. Tandy, No. 2 Company, Western Division, R.G.A., was specially mentioned to me for his services when detached with two 12-pr. Q.F. guns with a column under Lieut.-Colonel E. C. Bethune, 16th Lancers."[7] The war ended in June 1902, and Tandy returned to the United Kingdom on the SS Syria two months later, arriving in Southampton in early September.[8]
By 1904, Tandy was a captain and he was appointed adjutant at the Ordnance College at Woolwich in that year.[9] By 1915, he was a major within the Royal Artillery and the following year he was a temporary lieutenant-colonel, having been assigned as a general staff officer, grade 1.[10][11][12] At the end of the First World War he was temporarily promoted to be a brigadier-general and by this time he was invested with the Distinguished Service Order[13] and was invested as a Companion of the Order of St Michael and St George.[14]
The temporary elevation ended at the end of 1919 and Tandy retired from the army in 1921 and was placed in the reserve of officers with the honorary rank of brigadier general.[15][16] He was granted the temporary rank of colonel commandant while employed in India as a surveyor general.[17]
He finally retired from the reserve list in 1934.[18] He was a younger brother of Maurice Tandy.