In 1916, Horace Valentine Fuller was 24 and working as a clerk in Forest Hill. As a single man in his twenties, he was among the first group of men called up under the Military Service Act 1916 as conscripts, and his application for exemption must have been one of the earliest received by the Lewisham Tribunal.

His appearance before the Military Service Tribunal was reported in the Lewisham Borough News on 17 March 1916. Horace was a religious CO, who believed strongly that his Christian principles were opposed to warfare. He was reported as saying he had attended Torridon Road Congregational Church until the sermons preached there had become too militant and he had found them morally wrong - and by March he had moved to attending a more pacifistic church, Trinity Congregational. His application was unsuccessful as he was only passed for Non-Combatant duties. To a man such Horace, this was essentially the same as refusing his application altogether and he made it clear that he would appeal against the decision.

He was conscripted into the Non-Combatant Corps and was court-martialled for the first time on 13 June 1916 when he was sentenced to nine-months hard labour. On 4 August 1916 he was accepted as a genuine conscientious objector by the Central Tribunal at Wormwood Scrubs. He was not, however, given an unconditional exemption, but was sent instead to road mending at Risbridge House, Clare, Kedington West Suffolk under the Home Office Scheme. He spent nine months working under the scheme, but eventually he rejected its aims and methods, and was returned to the Non-Combatant Corps. Rejecting the Home Office Scheme meant that he would inevitably be returned to prison - through a second court martial for refusing orders while in the NCC. He was by now an absolutist, believing that any alternative service supported the war effort and conscription as well.

He was released by order of the secretary of state on 8 April 1919 having spent almost 2 years in prison mainly at Wormwood Scrubs and Wandsworth. Conscientious Objectors still in prison in April 1919 were released under what became known as the “Two Year Rule”, whereby all prisoners convicted of army offences would be released if they had served two years or more.

After the war, Horace was received into membership of the Kingston Quaker Monthly meeting on 19 June 1918 and married Henrietta Charlotte Light Abbott on 11 September, 1926, the sister of another CO George Stevens Abbott (1888-1969) that Horace met while on the Home Office Scheme in 1916.