Dion Williams was born at Williamsburg, Ohio, on 15 December 1869. He was appointed a Naval Cadet on 16 July 1887, and graduated from the U.S. Naval Academy, 30 June 1891, after which he served aboard the USS Atlanta for two years as a Midshipman in the Navy. He was commissioned a Second Lieutenant in the Marine Corps on 1 July 1893, and his subsequent promotions have been as follows: first lieutenant, 30 June 1894; captain, 3 March 1899; major, 28 February 1905; lieutenant colonel, 10 November 1914; colonel, 29 August 1916; and brigadier general, 3 June 1924.

From 1893 until 1897 he served at the Marine Barracks at Washington D.C., New York, and Mare Island, California, and in 1898 served aboard the USS Baltimore, which took part in the battle of Manila Bay on 1 May 1898, under Admiral Dewey. After that battle, under the orders of Admiral Dewey, he landed at the Spanish Navy Yard at Cavite, Philippine Islands, in command of a company of Marines. This company occupied the navy yard and town of Cavite and hoisted the American flag, this being the first American flag raised over Spanish soil in the Spanish soil in the Spanish-American War. For this duty he was officially commended by Admiral Dewey.

Following the Battle of Manila Bay he served in the Philippine Islands for two years aboard the USS Baltimore, USS Olympia and USS Oregon taking part in numerous operations afloat and ashore during the Spanish-American War and Philippine Insurrection.

From October 1900 until September 1902, he served at the Marine Barracks, Boston; from September 1902 until December 1902, he commanded a company in a battalion of Marines on the Isthmus of Panama for the protection of American interests and the Panama railroad during a revolution in the Republic of Colombia, from which duty he was transferred to the Island of Culebra, Puerto Rico, for duty as Adjutant of a force of Marines engaged in Advance Base maneuvers with the Atlantic Fleet.

From January 1903, until October 1904, he was Fleet Marine Officer of the U.S. Atlantic Fleet, aboard the USS Kearsarge in Atlantic and European waters. From January 1905, until October 1906, he was on duty at the U.S. Naval War College at Newport, Rhode Island, as a member of the Staff of Instructors at that institution.

From October 1906, until November 1907, he served with the Army of Cuban Pacification in Cuba as Assistant to the Chief Engineer of that Army in supervising the work of making a rapid military survey of the Island of Cuba. For this work, he was officially commended by Major General J. Franklin Bell, Chief of Staff of the U.S. Army, and by the Chief Engineer of the Army of Cuban Pacification.

From December 1907 until October 1909, he was Fleet Marine Officer of the U.S. Atlantic Fleet, and Chief Intelligence Officer of that Fleet. During this time, the Fleet made the memorable cruise around the world by order of President Roosevelt. For the performance of duties during this cruise he was officially commended by Admiral Robley D. Evans, Admiral C.S. Sperry and Admiral Seaton Schroeder.

From November 1909 until March 1913, he was staff intelligence Officer in the Office of Naval Intelligence at Washington, D.C., and on intelligence duty in foreign countries.

From April 1913 until October 1915, he was Commandant of the Marine battalion stationed at the American Legation, Peking, China, for the protection of the Legation and the American citizens in the vicinity of Peking, and during a part of this time he was Senior Commandant of all of the foreign Legation Guards stationed at Peking.

From May 1915 until September 1918, he was on duty in the General Board of the Navy at Washington, D.C., from where he was transferred to Quantico, Virginia, where he commanded the Tenth Regiment of Marines until April 1919.

From April 1919 until May 1921, he served with the Second Brigade of Marines in Santo Domingo, as Commandant of the Northern District and commanding officer of the Fourth Regiment of Marines. During this time he received numerous letters of commendation from the Secretary of the Navy, Major General Commandant of the Marine Corps, Military Governor of Santo Domingo and Commanding General of the Second Brigade of Marines for the performance of duty.

He was attached to Headquarters, Marine Corps from May 1921 until August 1921, when he was ordered to the Army War College at Washington, D.C., from which institution he graduated in July 1922.

From July 1922 until August 1924, he was attached to the Marine Barracks, Quantico, commanding the Fourth Brigade of Marines from July 1924 until January 1925, and as commanding general of the Marine Barracks, Quantico, from April 1924 until August 1924.

From January to March 1924, he commanded the Marine Corps Expeditionary Force which occupied the Island of Culebra during the Winter Maneuvers of the U.S. Fleet, for the performance of which duty he received the official commendation of the Admiral of the Fleet and the Major General Commandant of the Marine Corps.

In August and September 1924, he was commanding general of the Marine Corps Expeditionary Force from Quantico which marched through Virginia and Maryland to the Battlefield of Antietam, where the Force was exercised in field exercises under simulated war conditions, culminating in a demonstration of a modern attack of all arms of National Defense Day. On 22 September 1924, the Major General Commandant commended BGen Williams on the precision and smoothness with which the Force functioned during these maneuvers, indicating a pains-taking preparation, an efficient staff system and a high degree of military training, which reflected great credit on BGen Williams as Commanding General, and on the officers and men attached to the Force.

From September 1924 until July 1925, he was Director of Operations and Training at Headquarters of the Marine Corps, Washington, D.C., and after that time he served as Assistant to the Major General Commandant of the Marine Corps.

In April and May 1925, he was commanding general of the Second Marine Division of the Marine Expeditionary Force which accompanied the U.S. Fleet in the Joint Army and Navy exercises in the Hawaiian Islands.

Brigadier General Williams died Thursday, 11 December 1952 at the Naval Hospital, Bethesda, Maryland. He was buried with full military honors at Arlington National Cemetery on 15 December 1952.