Stanley enlisted on 6th May 1915 and was embodied into the 3rd East Anglian Field Ambulance, Territorial Force. He was 25 years old at the time. On 30th March 1917 he was transferred to serve with the regular army, R.A.M.C., his service number changing from 2471 to 93499. On 16th April 1917 he arrived for active service in France. He gained promotion to the rank of corporal on 1st November 1918, then was appointed acting sergeant on 19th August 1919. The following month, on 26th September he was promoted again to temporary sergeant. He was discharged from the army on 28th November 1919, having suffered impairment since entry into the service. This was due to him contracting sinews in his right leg and decaying muscles.