Second Lieutenant William Garrett Mercier
William Garrett Mercier was born on 1 March 1883 at Cuddagh, Castletown, Queens County, one of eleven children of American-born farmer William Mercier and his wife Elizabeth (nee Garrett). Educated at Agharoe National School, Queens County, privately by the Reverend H. Paul at Ballycolla, and at Skerry's Business Training College, Dublin, by the time of the 1911 Census he was living with three of his sisters at 71 South Parade, Belfast, and working as a cashier for the Bank of Ireland.
Mercier enlisted in the North Irish Horse at Antrim on 14 January 1915 (No.1400 – later Corps of Hussars No.71373), understating his age by two years. He was promoted to lance corporal on 3 March, corporal on 28 April, lance sergeant on 28 July and sergeant on 18 November 1915. On 11 January 1916 he embarked for France with E Squadron.
On 15 November 1916 he was appointed acting squadron quartermaster sergeant – he was confirmed in that rank on 8 January 1917.
In February 1918 the 1st North Irish Horse Regiment, of which E Squadron was a part, was dismounted and converted to a cyclist regiment. This necessitated a 25 per cent reduction in the regiment's establishment. A number of the men were transferred to other regiments, while others, including Mercier, were asked to apply to be trained as officers. Mercier applied for a commission in the infantry, with a preference for the Royal Irish Fusiliers, on 23 February 1918, departing for the UK the same day. After being attached to the 15th Reserve Brigade at Belfast, on 10 May 1918 he reported for duty at the No.7 Officer Cadet Battalion at Fermoy.
After a period of training he was assessed as having a good standard of education and military knowledge, and "good control & command & generally sound" power of command and leadership. He was a "good type, hard worker and a leader" and "should make a useful officer".
Mercier was commissioned as a 2nd lieutenant on 30 October 1918 and posted direct to France to join the 5th (Service) Battalion, Royal Irish Fusiliers. He joined the battalion in the field on 26 November 1918 – fifteen days after the end of hostilities – and was posted to C Company.
Mercier left his battalion for the UK on 30 March 1919 – he was demobilised six days later. He relinquished his commission on 1 September 1921.
After the war Mercier resumed work with the Bank of Ireland, initially living at Ardene, Helen's Bay, County Down. On 24 April 1923 he married Lilian Callaghan. By 1954 he was living with his wife at 61 King's Road, Belfast. He died at the Royal Victoria Hospital on 14 September that year.