During World War I, on August 13, 1918, the 31st moved from Fort William McKinley to Manila, and there set sail for Vladivostok, Siberia, arriving on August 21. The regiment was then broken into various detachments and used to guard the Trans-Siberian railroad, as well as 130 km of a branch line leading to the Suchan mines[?].
The regiment suffered it's first battle casualties on August 29, 1918, in action near Ugolnaya[?]. During the Siberian deployment, 30 soldiers of the 31st INF were killed (including 1 officer) and around 60 troops were wounded in action. In addition, a large number of troops lost a limb, due to frostbite[?]. During this deployment, the regiment received 1 congressional medal of honor[?] and 15 Distinguished Service Crosses[?].
On February 1, 1932, the regiment was ordered to Shanghai, China, arriving on February 4. There, the unit guarded a section of the International Settlement[?], amongst considerable fighting between Japanese and Chinese troops. On July 5, 1932, the unit returned to the Philippines.
The 31st Infantry Regiment was created from elements of the 8th[?], 13th[?], 15th[?], and 27th Infantry Regiments[?]. The 1st Battalion was formed at Regan Barracks[?], the 2nd at Camp McGrath[?], and the 3rd at Fort William McKinley.