Upon completion of the torpedo course, Fitch helped to fit out the battleship Delaware, which commissioned on April 4, 1910, before returning to Annapolis for consecutive tours of duty at the Naval Academy, first as assistant discipline officer between 1911 and 1912 and later as an instructor of physical training from 1912 to 1913.

Relieved of command of Yankton shortly after the United States entered World War I in the spring of 1917, Fitch continued his staff duties for another five months before joining Wyoming to serve as her gunnery officer for the remainder of hostilities, as that dreadnought operated with the 6th Battle Squadron, Grand Fleet.

Detached from Mahan in December 1922, Fitch served at Rio de Janeiro until March 1927 as a member of the United States mission to Brazil before reporting back to the Navy Department for a brief tour of duty in Washington, D.C.

Fitch's flagship, Saratoga, figured prominently in the abortive attempt to reinforce Wake Island in December 1941 and was later torpedoed off Oahu in late January 1942, seriously cutting American carrier strength in the Pacific at a critical period.

That engagement, the first in history where neither side came within surface gun range of the other, effectively stopped the Japanese thrust at the strategic Port Moresby, but resulted in the first loss of an American aircraft carrier in the war— the USS Lexington, sunk on May 8, 1942.

Fitch together with Captain Frederick C. Sherman and the Lexington's executive officer, Commander Morton T. Seligman, visited "Lady Lex"'s wounded in Minneapolis' sickbay—an action that "contributed in no small measure to the patients' well-being."

Under Fitch's command, AirSoPac—ultimately encompassing not only Navy but Army, Marine Corps, and Royal New Zealand air units—achieved great success in aiding the Allied campaign in the South Pacific.

Later, Fitch oversaw the early experiments in conducting night bombing utilizing radar (a concept which paid great dividends in interdicting Japanese shipping) and encouraged the use of specially modified aircraft to obtain photographic intelligence.

He skillfully and efficiently directed the aeronautical organization of the Navy, oversaw efforts to assure the readiness and deployment of air units, and planned all of the related logistics measures.

Subsequent to heading the academy, Fitch served briefly in the Office of the Undersecretary of the Navy before becoming the senior member of the Naval Clemency and Prison Inspection Board in March 1947.