He was most notable for leading his brigade to victory during the September 1918 Battle of Montfaucon, part of the first phase of the Meuse-Argonne Offensive, for which he received the Distinguished Service Cross.

After the war, he commanded the 152nd Depot Brigade, where he oversaw the demobilization and discharge of soldiers returning home after the Armistice.

[5] With the 7th Cavalry Regiment's officer corps depleted by the June 1876 Battle of the Little Bighorn, the organization moved quickly to replenish the ranks of its lieutenants and captains.

[6] He took part in the final stages of the Little Bighorn Campaign, including the Battle of Canyon Creek against the Nez Perce Indians in September 1877.

[8] Nicholson was a noted horseman and during his career he took part in numerous equestrian activities, including stakes races, polo matches, and horse shows.

[6] In January 1884, he was promoted to first lieutenant in the 7th Cavalry's Troop M.[12] From 1884 to 1887, he served as professor of military science and tactics at Kansas State University.

[13][14] In October 1888, Nicholson was assigned to Troop G and was part of a 7th Cavalry contingent that marched from Fort Riley to Topeka, Kansas to participate in festivities at a week long reunion of Grand Army of the Republic members and members of the Military Order of the Loyal Legion of the United States.

[19] Based at Fort Monroe, he was responsible for enrolling National Guard members and civilians who volunteered for army service.

[19] He was promoted to temporary major in July 1898 and attached as ordnance officer on the staff of 2nd Division, First Army Corps.

[23][24] During his tenure, Nicholson took steps to curb the grazing of herds on Indian land without permission, a practice in which many white Arizonans were involved.

[35] From November 1913 to February 1915, Nicholson was commander of the 2nd Cavalry Regiment, based at Fort Ethan Allen, Vermont.

[36][37] From 1915 to 1916, Nicholson planned and organized the instruction of military-minded civilians as commander of the Citizens' Military Training Camp at Fort Sheridan, Illinois.

[43] The brigade included the 313th and 314th Infantry Regiments, as well as the 311th Machine Gun Battalion, and it completed its initial organization and training at Camp Meade, Maryland.

[47] During the fighting, Nicholson personally located and traveled on horseback to the 79th Division’s headquarters to arrange for artillery support to the 313th Infantry.

[48] Nicholson remounted his horse and road forward to his brigade headquarters, where he issued orders to continue the attack on Montfaucon, directed his staff’s planning, supervised unit preparations, and then led the renewed action that finally captured the objective.

[54] At age 62, Nicholson was the oldest American soldier known to have seen combat during World War I – the few generals older than him, including Hugh L. Scott, Tasker H. Bliss and William Abram Mann, served in training, staff, and administrative roles.

[57] In retirement, Nicholson was a resident of Washington, D.C.[55] In September 1920, he was elected president of the Army and Navy Club of America.

[6][55] 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 William Jones Nicholson, United States Army, for extraordinary heroism in action while Commanding the 157th Infantry Brigade, 79th Division, A.E.F., near the Bois-de-Beuge, Montfaucon, France, 29 September 1918.

In the face of this terrific fire General Nicholson, with great coolness and with complete disregard for his own safety, rode forward on horseback to his brigade post of command to issue orders for the renewed attack upon the Madeleine Farm, supervised the formation for attack, and by his brave and gallant example inspired the men of his command with renewed courage and determination, which enabled them to reach their objective and hold it against repeated enemy counterattacks.