in the patrols along the Mexican border during Pancho Villa Expedition. In July 1915, Brush was transferred to the United States Disciplinary Barracks at Fort Leavenworth, Kansas and joined First Company of local Guard Battalion. He was promoted to first lieutenant in July 1916 and assumed duty as Adjutant of 1st Disciplinary Battalion at Fort Leavenworth under Major Dwight W. Ryther. Upon the United States' entry into World War I, Brush was promoted to Captain in May 1917 and assumed duty as Barracks Adjutant, United States Disciplinary Barracks at Fort Leavenworth. He was promoted to the temporary rank of Major in June 1918 and joined 53rd Infantry Regiment at Camp Forrest, Georgia. Brush participated in the training of new recruits and formation of new units at Camps Pike and Wadsworth, South Carolina and did not deployed overseas during World War I. Interwar period Following the Armistice, Brush was transferred to the War Department General Staff in Washington, D.C. and joined the Publication Division of the Adjutant General's Department. He served there for two years and his rank of Major was made permanent during that time. He was transferred to the Training Center of Ninth Corps Area at Presidio of San Francisco, California in October 1920 and served as Post Adjutant under Brigadier general Chase W. Kennedy until his departure for the instruction at the Army Command and General Staff School at Fort Leavenworth, Kansas in August 1922. Brush graduated as Distinguished Graduate in June 1923 and returned to the Presidio of San Francisco for duty as an Instructor, Organized Reserves, Ninth Corps Area. In September 1925, Brush was ordered to the Army War College in Washington, D.C. and upon graduation following June, he assumed duty as Commanding Officer, 2nd Battalion, 13th Infantry Regiment at Fort Devens, Massachusetts. He was later transferred to the Fort Strong, Massachusetts and served as Commanding Officer, 1st Battalion his regiment until August 1927, when returned to Washington, D.C. Brush was subsequently assigned to the Office of the Assistant Chief of Staff for Operations (G-3) and served consecutively under Brigadier generals Frank Parker and Edward L. King until May 1931, when he was transferred to Vancouver Barracks, Washington for duty with 7th Infantry Regiment. While in this capacity, he served again under Colonel Dwight W. Ryther, a decorated veteran of Spanish-American War whom he met during World War I and also with Charles H. Corlett future