Findlay was born on 7 May 1859 in Lanarkshire, Scotland, the son of Thomas Dunlop Findlay of Easter Hill. He entered the Royal Military Academy, Woolwich as a gentleman cadet in January 1878 and was commissioned as a lieutenant in the Royal Artillery on 18 December 1878. Findlay was promoted to captain on 23 July 1887 and served in the Hazara Expedition of 1888 in British India where he was mentioned in despatches. He had spent some time at the Staff College, Camberley prior to the Hazara Expedition. On 1 March 1894, Findlay was made adjutant. He was promoted to the rank of major on 21 December 1896, and transferred into the Royal Field Artillery when that branch was created on 1 July 1899. He served in the Second Boer War, seeing action in Natal and Transvaal and taking part in the Relief of Ladysmith. Findlay commanded Lieutenant-General Redvers Buller's ammunition column and was mentioned in despatches on two occasions. He received the Queen's South Africa Medal with six clasps for his participation in the campaign. Buller was impressed with Findlay's performance, and stated that he considered "Major Findlay one of the best Officers I met. He was an admirable commander of an Ammunition Column, loaded with ammunition of many different natures. His batteries were complete every night, and he never made a mistake. He has all the qualifications for the staff and for high command, and I desire to bring his name most prominently to your notice as deserving of all consideration." Shortly after this commendation was published in the London Gazette on 8 February 1901 Findlay was appointed a staff officer.
Findlay was promoted to brigadier general on 25 August 1914, shortly after the outbreak of the First World War on 28 July 1914. He served with the 1st Infantry Division in France as Commander, Royal Artillery and fought with them at the First Battle of the Aisne. German forces held the high ground on the east of the Aisne valley and a Franco-British offensive was planned to dislodge them. British forces advanced at dawn on 10 September to attempt a river crossing at Venizel in support of French forces fighting at Soissons. A French Zouave unit simultaneously crossed at Villesur Aigue to threaten the German right flank. The British troops encountered heavy resistance from the German rearguard, an all-arms force which was holding a ridgeline near Preuil, and the British artillery, commanded by Findlay and stationed at Priez, was brought into action. German siege howitzers opened fire on Findlay's artillery and the road adjacent to his position, though few deaths were caused as the shrapnel shells exploded too high at. The position was, however, in danger of being overrun by German forces and Findlay ordered his guns brought into action for immediate defence. He then approached his regimental chaplain, gave him some of his personal belongings and requested he look after them in case anything happened to him. Findlay remained with his artillery pieces, providing advice and encouragement to the gun crews, against the advice of his staff who asked him to move to a place of safety. The British artillery was winning the artillery duel, causing the German fire to slacken and allowing the infantry to advance. At this point a parting shot from the Germans struck Findlay's horse, killing both. Findlay was struck by shrapnel near his left eye. The German fire may have been directed at a unit of British infantry which was passing along the road adjacent to Findlay's position at the time. Findlay was selecting a new position for his guns near Torey north of Chateau Thierry when he was killed. By that afternoon the allied infantry had successfully crossed the river and forced the Germans to retreat to Laon and La Fère. Findlay, the first British general to be killed in the war and described as one of the army's best artillery officers, was buried at the churchyard in Courchamps under a bronze cross. His body was exhumed and moved to Vailly British Cemetery on 15 June 1938. His replacement with the 1st Infantry Division was Brigadier General Edward Fanshawe, who later became a corps commander. There is a plaque in his memory at Kenmuir Mount Vernon Church in Kenmuir near Mount Vernon, Glasgow. Findlay was married to Alma Lloyd and had two daughters.
