Stark served on the staff of Commander, United States Naval Forces operating in Europe from November 1917 to January 1919.

He also orchestrated the navy's change to adopting unrestricted submarine warfare in case of war with Japan;[2] Stark expressly ordered it at 17:52 Washington time on 7 December 1941,[3] not quite four hours after the Japanese attack on Pearl Harbor.

He received the additional title of Commander of the Twelfth Fleet in October 1943, and he supervised USN participation in the landings in Normandy, France, in June 1944.

Forrestal concluded that both Kimmel and Stark had "failed to demonstrate the superior judgment necessary for exercising command commensurate with their rank and their assigned duties.

[15] Stark's most controversial service involved the growing menace of Japanese forces in the period before America was bombed into the war by the attack on Pearl Harbor.

In his book, And I Was There: Pearl Harbor and Midway – Breaking the Secrets (1985), Layton maintained that Stark offered meaningless advice throughout the period; withheld vital information at the insistence of his Director of War Plans, Admiral Turner; showed timidity in dealing with the Japanese; and utterly failed to provide anything of use to Kimmel.

[16] John Costello (Layton's co-author), in Days of Infamy (Pocket, 1994), points out that Douglas MacArthur had complete access to both PURPLE and JN-25, with over eight hours warning, and was still caught by surprise.

Moreover, as the Supreme Commander of the Allied Powers official historian Gordon Prange and his colleagues note in December 7, 1941 (McGraw-Hill, 1988), the defense of the fleet was General Walter C. Short's responsibility, not Kimmel's.

In addition, there was considerable confusion over where Japan might strike: the United States, the Soviet Union, or British colonies in Asia and the Far East.

[21] Stark maintained a family summer residence on Lake Carey in Tunkhannock, Pennsylvania, north of his native Wilkes-Barre, for many years and flew in by naval seaplane for weekends during his career.