[9] Among his classmates who also became general officers were Thomas Q. Ashburn,[10] Andrew Moses,[11] Harry Gore Bishop,[12] Frank Ross McCoy,[13] Harold Benjamin Fiske,[14] Albert Jesse Bowley Sr.,[15] Harley Bascom Ferguson,[16] Sherwood Cheney,[17] and William Durward Connor.

[20] From January to July 1900, he was posted to Columbia Barracks near Havana, where he served with the 8th Infantry during the United States Military Government in Cuba.

[21] He served with his regiment at Fort Snelling, Minnesota from July to September 1900, then departed for the Philippines, where he took part in several skirmishes on Luzon during the Philippine–American War.

[21] When he returned to the United States in late 1906, Collins was assigned to duty with the 6th Infantry at Fort William Henry Harrison, Montana.

[22] From March 1909 to June 1910, Collins was posted to Fort Leavenworth to attend the Army School of the Line, which he completed as an honor graduate.

[23] He was then enrolled as a student at the United States Army Command and General Staff College, from which he graduated in June 1911.

[23] Collins commanded Company F, 10th Infantry in Panama until May 1916, in addition to performing temporary staff duty with the Citizens' Military Training Camp (CMTC) at Plattsburgh Barracks, New York in the summer of 1915.

[23] In August 1917, he was promoted to temporary lieutenant colonel and assigned to duty on the staff at the United States Department of War.

[23] Upon his return to the United States, he was promoted to temporary colonel as chief of staff of the 85th Division during its training and organization at Camp Custer, Michigan.

[23] After the division arrived in France in August 1918, Collins was assigned to the training section (G-5) on the staff of the American Expeditionary Forces.

[23] Collins remained on duty in Europe during the Occupation of the Rhineland, and served on the AEF's Infantry Board, which considered wartime lessons learned and developed recommendations for future equipment, weapons, and training.

[25] He was promoted to brigadier general in November 1924, and in February 1925 he was assigned to command the 1st Field Artillery Brigade at Fort Hoyle, Maryland.

[5] His funeral took place at the Fort Myer chapel, and was conducted by Julian E. Yates, the army's Chief of Chaplains.

[27] Honorary pallbearers included Douglas MacArthur, George Van Horn Moseley, Robert Emmet Callan, John W. Gulick, and Andrew Moses.

As Assistant to G-5, General Headquarters, and later as Chief of Staff of the 6th Army Corps, Colonel Collins demonstrated rare military attainments, performing his difficult tasks with unremitting zeal, rendering services of conspicuous worth to the American Expeditionary Forces.