During World War II he received the second highest American military award, Distinguished Service Cross, for his leadership of the 2nd Infantry Division during the Battle of the Bulge in December 1944.

[3][2] In early 1916, Robertson was transferred to Fort Missoula, Montana, where he served for few months, before he was ordered to the newly established officer training school at Camp Bullis in Texas.

He assumed command of 9th Infantry Regiment in November that year and remained in that capacity until the United States' entry into World War II, following an Attack on Pearl Harbor in December 1941.

[3][1][5] After he assumed command, he led division during the four-month intensive training in winter warfare at Camp McCoy, Wisconsin, and embarked for England in October 1943.

Robertson then led his division during another period of training in Northern Ireland and Wales and finally deployed to France on Omaha Beach on D-Day plus 1 (June 7, 1944) near Saint-Laurent-sur-Mer.

As reinforcements arrived, Robertson proceeded immediately to a second critical area where another salient was threatening two villages along the main route of the enemy advance.

He organized troops from his own command and stragglers from elements overrun by the powerful attack and, for a period of seven hours, heroically led them in deterring the advance.

[6][2] Constantly exposed to intense fire from tanks, machine guns and small arms, Robertson, by his personal direction and his calm and collected demeanor, successfully rallied his men to hold their ground tenaciously.

His presence among the foremost elements of his command, his exemplary courage and his self-assurance were primarily responsible for knitting the scattered troops into a cohesive fighting force and checking the forward drive of the enemy spearhead.

The citation for the medal 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 Major General Walter Melville Robertson (ASN: 0-3378), United States Army, for extraordinary heroism in connection with military operations against an armed enemy while Commanding the 2d Infantry Division, in action against enemy forces on 17 December 1944, in Belgium.

As reinforcements arrived, Major General Robertson proceeded immediately to a second critical area where another salient was threatening two villages along the main route of the enemy advance.

He organized troops from his own command and stragglers from elements overrun by the powerful attack and, for a period of seven hours, heroically led them in deterring the advance.

Constantly exposed to intense fire from tanks, machine guns and small arms, Major General Robertson, by his personal direction and his calm and collected demeanor, successfully rallied his men to hold their ground tenaciously.

His presence among the foremost elements of his command, his exemplary courage and his self-assurance were primarily responsible for knitting the scattered troops into a cohesive fighting force and checking the forward drive of the enemy spearhead.

He held that office during the early years of the Cold War and Robertson's main task was to prepare the people of California for the possible atomic bomb attacks.

His honorary pallbearers were his West Point Classmates: Stephen J. Chamberlin, Roscoe C. Crawford, Wade H. Haislip, Robert M. Littlejohn and Sidney P. Spalding.