The son of a career Army officer, Glassford graduated from the United States Military Academy in 1904 and was commissioned in the Field Artillery.

Following his military retirement, Glassford was Superintendent of the District of Columbia Police, a position he resigned because of disagreement over the actions taken against the Bonus Army in 1932.

During World War II, Glassford returned to active duty and served for nearly two years in the office of the Provost Marshal General.

[2] Upon arrival in France with his regiment, Glassford was promoted to temporary lieutenant colonel and assigned as secretary of the Field Artillery School of Instruction in Saumur.

[1] Glassford trained his brigade to become proficient in the technique of reloading on a cannon's recoil; while this practice posed risk to crew members who might be injured by the moving recoil mechanism, it enabled 26th Division artillery crews to shoot so fast that German soldiers were convinced the Americans had automatic fire artillery pieces.

[2] He returned to the United States with his brigade in July, reverted to his permanent rank of major, and was assigned to the office of the Chief of Field Artillery.

[2] Glassford subsequently returned to the War Department staff and served as chief of the Mobilization Branch in the Operations and Training Division.

[2] Glassford worked to accommodate them, visiting their leaders daily by motorcycle to help maintain order, and arranging for volunteers to provide medical care, as well as donations of food, clothing, tents, and other supplies.

[1][6] Favorable Congressional action was not forthcoming, and many Bonus Army members accepted the government's offer of free transportation home.

[6] Glassford managed to obtain a six-day extension before enforcement, hoping to persuade the Bonus Army members to depart voluntarily.

[2] Glassford's police began to execute the order; they were met with resistance, and during an exchange of shots, two veterans were wounded and later died.

[2] General Douglas MacArthur, the Chief of Staff of the Army, took personal command of infantry and cavalry units, which were supported by six tanks.

[2] Glassford had established a positive relationship with leaders of the Bonus Army, and disagreed with Hoover and Mitchell about the need to eject the members and destroy the campsites.

[2] The Board of Commissioners for the District of Columbia held Glassford responsible for the violence and refused to allow him to name appointees who agreed with his policies.

[2] He mounted a brief run for governor of Arizona in 1934,[8] and also that year accepted a federal appointment to mediate labor-management disputes between workers and owners of lettuce and cantaloupe farms in Imperial Valley, California.

[11] The temporary appointment came with a mandate to reorganize and reform the department to end corruption and outside political influence, and restore morale.

[2] They were the parents of four children: Guy Carleton (1908–1974), Cora Elizabeth (Mrs. Lee Parke) (1910–1986), Pelham Davis (1911–1992), and Dorothy Seymour (Mrs. William Graham) (1913–1977).