Shell was commissioned a second lieutenant in the Marine Corps the same month and assigned for officers training to the Basic School at the Philadelphia Navy Yard.

He was attached to the Marine detachment aboard the newly commissioned heavy cruiser USS Astoria in March 1934 and took part in the shake-down cruise in the Pacific Ocean with the stops at Samoa, Fiji, New Caledonia, Australia and Hawaii.

He was promoted to the rank of captain in July 1938 and assigned to the Battery Commanders' course at Field Artillery School at Fort Sill, Oklahoma in September of that year.

Shell served with 2nd Battalion until September 1940, when he was appointed commanding officer of the Marine detachment aboard the patrol gunboat USS Charleston.

Meanwhile, Shell was appointed commanding officer of 2nd Battalion and led it overseas as a part of 2nd Marine Division under Major General John Marston in October 1942.

Along with the rest of the 10th Regiment, the battalion then sailed back to New Zealand for recuperation and Shell was promoted to the rank of lieutenant colonel the next month.

[4][5][6] In July 1946, Shell attended Naval War College in Newport, Rhode Island, and upon graduation in June 1947, was appointed an instructor there.

He was ordered to Paris, France in February 1951 and appointed Staff Planning Officer in the Policy Branch within Operations Division at Supreme Headquarters Allied Powers Europe.

Other members of the group were Thomas J. Coolley, John P. Condon, August Larson Joseph N. Renner, Carson A. Roberts, Samuel R. Shaw, Eustace R. Smoak, William J.

[7][8] Shell was ordered to the headquarters of Fleet Marine Force Atlantic at Norfolk, where he was appointed chief of staff under Lieutenant General Oliver P. Smith in July 1954.