Sydney Naylor was commissioned as a Second Lieutenant in the 9th Battalion Manchester Regiment (Territorial Force) on November 7, 1914 and was quickly appointed Temporary Lieutenant two weeks later. He joined the 2/9th Battalion in training at Southport and moved with them to Pease Pottage in June 1915. On October 13, 1915 he embarked for Gallipoli with 10 other Officers, arriving at Mudros on October 24th and joined the Battalion on Cape Helles on October 26, 1915. Upon arrival it was found that two Officers already serving at Gallipoli were of a junior rank and so he relinquished his temporary appointment. On November 29, 1915 he was wounded and evacuated to hospital at Mudros and sometime later was invalided to the UK.
In England, he rejoined the 3/9th Battalion at Codford in January 1916. He rejoined the 1/9th Battalion in Egypt on October 25, 1916 and within 3 days reported sick to hospital. On November 12, 1916 he was promoted to Lieutenant and was attached to the 1st Garrison Battalion, The Devonshire Regiment and struck of the strength of the Battalion. He evidently did good work because he was awarded the Military Cross in the King’s Birthday Honours List on May 31, 1918. And on June 24, 1918 he was awarded a commission as a Lieutenant in the regular forces with the Duke of Wellington’s Regiment (West Riding).
During the inter-war years he was appointed Adjutant and temporary Captain of the 6th Battalion Duke of Wellington’s Regiment (West Riding) on January 31, 1927. He was appointed Staff Captain and served as Adjutant to the 3rd Battalion and 6th Battalion the Duke of Wellington’s Regiment (West Riding). In 1934 he was promoted to Battalion Major and on May 26, 1936 he retired from the Army but remained on the Reserve Officers List. He served in the second world war and in 1946 ceased to belong to the Reserve of Officers, having exceeded the age limit but retained the honorary rank of Colonel. In January 1947 he was awarded the Legion of Merit, Degree of Officer by the President of the United States of America for services in the cause of the Allies.