While living in Black Hawk, Littleton enlisted in the Marine Corps Reserve on July 29, 1948, for a one-year term and took recruit training in San Diego, California.

[8] By doing so, he saved the lives of the other three Marines including the officer and forward observer in charge of Littleton's team during the early morning enemy counterattack on C Company.

The President of the United States of America, in the name of Congress, takes pride in presenting the Medal of Honor (Posthumously) to Private First Class Herbert A Littleton (MCSN: 1084704), United States Marine Corps Reserve, For service set forth in the following citation: for conspicuous gallantry and intrepidity at the risk of his life above and beyond the call of duty on 22 April 1951, while serving as a radio operator with an artillery forward observation team of Company C, First Battalion, Seventh Marines, FIRST Marine Division (Reinforced), in action against enemy aggressor forces near Chungchon, Korea.

When an enemy hand grenade was thrown into his vantage point shortly after the arrival of the remainder of the team, he unhesitatingly hurled himself on the deadly missile, absorbing its full, shattering impact in his body.

By his prompt action and heroic spirit of self-sacrifice, he saved the other members of his team from serious injury or death and enabled them to carry on the vital mission which culminated in the repulse of the hostile attack.

His indomitable valor in the face of almost certain death reflects the highest credit upon Private First Class Littleton and the United States Naval Service.