In April 1909, he left Rhode Island and went to the General Electric Co. in Schenectady, New York, for a year of instruction.

By May 1917, he and his ship were conducting antisubmarine patrols and convoy escort missions in the western approaches to the British Isles.

Bagley and 37 others made it into the icy water in boats and on rafts, and, thanks to the humanitarian gesture by Kapitänleutnant Hans Rose, the U-boat commander who radioed their location to Queenstown, they were all picked up by the 8th.

Bagley returned to the United States after the sinking of Jacob Jones and became the prospective commanding officer of USS Lea (DD-118) then under construction at the Philadelphia Navy Yard.

At the end of the academic year in 1926, he left the academy to become chief of staff to the Commander, Naval Forces, Europe, embarked in USS Memphis (CL-13).

In May of that year, Rear Admiral Bagley began a 32‑month tour of duty as Commandant, Mare Island Navy Yard.

He was serving in that command billet when his flagship was slightly damaged on December 7, 1941, during the Japanese air raid on Pearl Harbor.

Promoted to vice admiral to date from February 1, 1944, he was relieved of duty as Commander, Western Sea Frontier, on November 17, 1944.

Eleven days later, Vice Admiral Bagley returned to Oahu and resumed duty as Commandant, 14th Naval District, and served in that position until ordered to Washington on July 25, 1945.

Bagley was relieved of all active duty on March 22, 1946, and was placed on the retired list with the rank of admiral on April 1, 1947.

Guests included Admiral Bagley, Governor Ingram Stainbackof the Territory of Hawaii, Brigadier General Littleton W. T. Waller Jr., USMC, and Commodore J. L.