[3] In February 1918, ten months after the American entry into World War I, Millikin was the executive officer (XO) of the U.S. Army General Staff College in Langres, France.

[1] He was promoted to the rank of lieutenant colonel on November 16, 1918, five days after the Armistice with Germany, and became chief of the military police of the American Expeditionary Forces (AEF).

As Executive Officer and Assistant Director of the Army General Staff College, at Langres, Lieutenant Colonel Millikin rendered conspicuous services.

Later, as Chief of the Military Police Corps Division of the Provost Marshal General's Department, American Expeditionary Forces, by his ability, untiring zeal, and wound judgment, he aided in a material way in producing an efficient organization.

The corps also participated in the "Red Ball Express" by organizing 45 provisional truck companies to carry fuel and ammunition for the units on the front lines.

[10] The forces to be employed for the relief of Bastogne had been earmarked as early as the night of December 18, 1944, when Bradley and Patton agreed to move the new III Corps headquarters (as yet inexperienced and untried) from Metz to Arlon.

Millikin received a second Army Distinguished Service Medal for his leadership in driving his forces through the German defenses to relieve the besieged troops in Bastogne.

"[14] In the last week of February, Colonel Charles G. Patterson, the anti-aircraft artillery officer for III Corps, led a meeting for brigade and group commanders during which they discussed what they would do if they were lucky enough to capture a bridge intact.

[15] On March 2, 1945, Major General Millikin assigned the 14th Tank Battalion commanded by Lieutenant Colonel Leonard E. Engeman to the north flank and attached it to the 1st Infantry Division.

[18] Hodges also complained later that Millikin had repeatedly disobeyed his orders including a directive to drive his forces north along the east bank and open a crossing for Major General J. Lawton Collins's VII Corps, and that he failed to attach enough infantry support to the 9th Armored Division.

[17] These political observations are offset by the awarding of a Silver Star to Millikin for his brave leadership in exposing himself to enemy fire to personally speed his troops across the river.