He entered the United States Military Academy (USMA) at West Point, New York, from where he graduated thirty of thirty-nine with the class of 1885.

Among his classmates included several men who would later rise to the rank of brigadier general or higher in their military careers, such as Joseph E. Kuhn, Charles H. Muir, John D. Barrette, Robert A.

[2][3] After completing a brief tour of duty with the 16th Infantry at Fort Douglas, Utah, he served as commandant of cadets at Baylor University from December 1893 to May 1895.

[5][6] After duty at Vancouver Barracks, Washington until March 1911, Buck served as assistant adjutant general of the Philippine Division in Manila until July 1912.

He subsequently joined the Massachusetts National Guard as an inspector-instructor from December 1914 to June 1917 preparing guardsmen for deployment to the US-Mexican border.

Buck was promoted to the rank of brigadier general on August 5 and succeeded Robert Lee Bullard, a West Point classmate of 1885, in command of the 2nd Brigade.

The citation for his DSC reads: The President of the United States of America, authorized by Act of Congress, July 9, 1918, takes pleasure in presenting the Distinguished Service Cross to Brigadier General Beaumont Bonaparte Buck, United States Army, for extraordinary heroism in action while serving as Commanding General, 2d Infantry Brigade, 1st Division, A.E.F., before and during the attack of Berzy-le-Sec, France, 21 July 1918.

When most of the officers of his brigade had fallen, General Buck, with contempt of personal danger, in spite of heavy artillery bombardment and machine-gun fire, traversed the front of his advancing forces, gave correct directions to his organization commanders and led the first wave of the culminating attack which stormed and captured the town.

[13] Buck spent his final years in San Antonio, Texas, where he died on February 10, 1950, at the age of 90, and was buried in Fort Sam Houston National Cemetery.