The head of U.S. Pacific Fleet at Pearl Harbor said Monday he had submitted a request to retire after being passed over for the position of commander of the U.S. Pacific Command.

Adm. Scott Swift, a Pacific expert in a time of extreme tension with North Korea, but also with several ship collisions involving overworked sailors and assets under his watch, was seen as a leading candidate for the Pacific Command job at Camp H.M. Smith now held by Adm. Harry Harris.

Both four-star admirals are highly respected; Harris is expected to step down and retire in the spring.

“I have been informed by the chief of naval operations that I will not be his nominee to replace Adm. Harris as the commander, U.S. Pacific Command,” Swift said in a release. “In keeping with tradition and in loyalty to the Navy, I have submitted my request to retire. I do so with great appreciation and gratitude for the honor of having served so many sailors and their families for what will be 40 years in January.”

Swift added, “Submitting this request now is done with an abundance of respect and admiration for the CNO and his leadership, as well as for the chairman (of the Joint Chiefs of Staff) and secretary of defense as both of them face the challenge of selecting someone to step into the leadership role Adm. Harris has filled with such distinction over the last three years.”

Nevertheless, it is an unusual public response to Chief of Naval Operations Adm. John Richardson by a high-ranking commander.

The U.S. Pacific Command covers half the globe and includes seven of the world’s 10 largest standing armies. About 375,000 U.S. military and civilian personnel are assigned to the command. The Pacific Fleet has 200 ships and nearly 1,100 aircraft.

Carl Baker, executive director of the Pacific Forum Center for Strategic and International Studies in Honolulu, said Swift, who became head of Pacific Fleet in 2015, may have become caught up in blame for the string of Navy ship accidents this year in the western Pacific — including two destroyers that collided with hulking merchant vessels in June and August, killing 17 U.S. sailors.

On Aug. 23, Swift relieved of command the head of the 7th Fleet in Yokosuka, Japan, Vice Adm. Joseph Aucoin, “due to a loss of confidence in his ability to command.”

A Sept. 19 U.S Government Accountability Office report found that “the Navy has increased deployment lengths, shortened training periods, and reduced or deferred maintenance to meet high operational demands, which has resulted in declining ship conditions and a worsening trend in overall readiness.”

“What comes to mind immediately is that while Swift wasn’t directly identified as being part of the problem with the 7th Fleet, clearly it’s part of his command, and so, there’s that relationship that exists there that he could very well be being held responsible for some of the activity that occurred,” Baker said.

The Navy may have felt “it’s time to look beyond the Pacific to bring in somebody new,” Baker added.

Swift also has been “fairly strident in his comments on China” and that nation’s activities in the South China Sea, he said. Harris, the overall Pacific commander, has made similar remarks.

Such criticism and calls for “freedom of navigation” operations in the contested waters may have gotten Swift crossed with the State Department, Baker said.

Swift said he has not requested a retirement date, “as there is much work to be done here in the Pacific area of responsibility.”

“Whether my timeline of remaining service is six weeks or six months, I will fill that time with the energy of an ensign and the wisdom drawn from the 140,000 sailors who report for duty every morning in the Pacific Fleet,” Swift said.

On May 27, 2015, Swift returned to his home state and relieved Harris as commander of the Pacific Fleet during a change of command ceremony on Joint Base Pearl Harbor-Hickam.

Swift was born in Hawaii when his father was stationed at Pearl Harbor. Harris said at the ceremony that Swift’s Pacific ties made him the perfect officer to replace him.

“There’s no person more suited to be the Pacific Fleet commander than Adm. Swift — former J3 (operations) at PACOM, former 7th Fleet commander and most recently the director of Navy staff,” Harris said at the time.

At the same change of command ceremony, Harris relieved Adm. Samuel J. Locklear III as commander of U.S. Pacific Command.

Current Vice Chief of Naval Operations Adm. Bill Moran and Adm. Philip Davidson, commander of U.S. Fleet Forces Command, are two names mentioned as possible replacements for Harris.

The U.S. Naval Institute News reported that Gen. Terrence O’Shaughnessy, who commands Pacific Air Forces at Pearl Harbor- Hickam, also is in the running. If O’Shaughnessy is selected, it would be a shake-up to the long line of admirals in charge of Pacific Command.