[1][2] Nominated by his congressman to attend the United States Military Academy at West Point, he graduated in 1892, and was assigned in June of that year as a 2nd Lieutenant to the 13th Infantry Regiment.

It was becoming evident to many army commanders, both in the United States and abroad, that draft animals—the sole source of transport away from railroad tracks—were highly vulnerable to modern artillery fire at ranges under 1,500 yards, especially when contained in slow-moving trains of horse-drawn carriages and heavy wagons.

[2] After the outbreak of war with Spain, Lt. Parker approached General William Rufus Shafter, commander of the U.S. expeditionary campaign being readied in Tampa, Florida, for the assault on Santiago, Cuba, and requested permission to form a Gatling Gun Detachment.

On May 27, Parker was given four of a consignment of fifteen brand-new ten-barrel Model 1895 Gatling guns in .30 Army caliber recently received from Colt's Arms Company.

[5][8] In order to save time, Parker also received permission from General Shafter to utilize men from the infantry regiments already in Tampa and assigned to the invasion.

On his own initiative, Parker developed his own table of organization to include gun carriages, crew schedules, ammunition loads, and draft animal requirements.

Parker's battery, consisting of four guns, carriages, and some 30,000 rounds of .30 Army ammunition, was given priority for disembarkation at Daiquirí, Cuba by General Shafter.

[10] After being officially mustered into service on June 30, 1898, the Gatling Gun Detachment was ordered to advance to El Pozo, the site of General Shafter's headquarters for the impending offensive.

[10] After being ordered to send his guns forward "to the best point you can find", Parker set up his remaining three Gatlings near the base of the San Juan Heights to provide covering fire for the advancing U.S. ground forces.

[5][12] Equipped with swivel mountings that enabled the gunners to rake Spanish positions, the three fast-firing[13] guns, firing at a range of 600-800 yards, expended approximately 18,000 cal.

[20] Parker then moved the two guns again to avoid counterbattery fire, where they were used at a range of 2,000 yards to kill and scatter the crew of a Spanish 160 mm (6.3-inch) artillery cannon.

As an instructor at the Army Machine-Gun School at Langres, France, Parker instructed AEF troops in the use of the machine gun, for which he received the Distinguished Service Medal.

[25][26] His fourth DSC citation states that he was receiving the award for extraordinary heroism in action: During the attack on the village of Gesnes Colonel Parker displayed great gallantry and fearlessness in leading and directing his front line with utter disregard for personal safety and urged his men forward by his personal example, all under heavy machine-gun, high-explosive, gas-shell, and shrapnel fire.

He was abreast of his front line until he fell, twice wounded, but thereafter remained in active command for a period of five hours, when he was relieved by the lieutenant colonel of his regiment.

Parker commanded Jefferson Barracks, Missouri, from March 15 to November 15, 1921, served at St. Louis as Chief of Staff, 7th Corps, Organized Reserves from January 15 to December 15, 1922.

Repeatedly he climbed upon the firing step of the trench, and, standing there with his back toward the enemy and with shell splinters falling about him, he talked to his men in such cool, calm terms as to reassure them and brace them up so that when he left they were in a cheerful state of mind and in better condition to ward against attack.1st Bronze Oak Leaf: On July 21, 1918, near Trugny, France, he made a personal reconnaissance over a front of about 2 kilometers on horseback in the face of enemy fire and determined the strength of the German forces to insure the most advantageous approach for his troops to attack.

Several times he was an inspiring figure to his men under a heavy artillery barrage and concentration of machine‑gun fire.2nd Bronze Oak Leaf: On July 25, 1918, on the road through La Fere Wood, between Beuvardes and Le Charmel, France, a battalion just coming into the line was halted, awaiting orders.

Immediately appreciating the situation, he twice rode down the line and back again at a slow walk, stopping to talk with the men; and thus by his fearless personal exposure to, and disregard of, danger, he promptly steadied the troops and prevented probable disorder at an important juncture.3rd Bronze Oak Leaf: For extraordinary heroism in action near Gesnes, France, Sept. 29, 1918.

He was abreast of his front line until he fell, twice wounded, but thereafter remained in active command for a period of five hours, when he was relieved by the lieutenant-colonel of his regiment.For exceptionally meritorious and distinguished services.

As an instructor in the Army Machine Gun School at Langres, by his tireless efforts he secured the necessary equipment and ably instructed a large student body in the technical handling of one of the most important fire power weapons developed in the present war, rendering services of great value to the American Expeditionary Forces.For gallantry in action against Spanish forces at the battle of Santiago, Cuba, July 1, 1898.