As the new Pacific sub force commander, Cassias will be responsible for more than 9,300 Navy and civilian personnel, 25 nuclear-powered attack submarines, seven ballistic missile submarines, two guided missile submarines, one support ship, and a deep salvage rescue vessel.

Home ports include Bangor, Wash; San Diego; Guam and Pearl Harbor. Seventeen Los Angeles-class attack subs are based in Hawai'i.

Adm. Walter F. Doran, commander of U.S. Pacific Fleet, said the strength of the submarine force is a "critical stabilizer" in the western Pacific, "and the vital nature of that role should not be understated, considering the state of the world in which we live today."

China's roughly 70 submarines include one ballistic missile submarine and five attack subs, North Korea has the world's fourth largest submarine fleet with 26 diesel subs, and Iran has six subs, according to The Heritage Foundation.

It is that military buildup, and a corresponding shift in emphasis from the Atlantic to the Pacific with the end of the Cold War, that Cassias, 51, will have to concern himself with.

Doran said Sullivan's tenure at the helm of the Pacific submarine force for the past two years has served the Navy well, and Cassias is the right man to continue the job.

"These two men have been stalwarts of the submarine force for decades, and they have contributed greatly to our pre-eminence in undersea warfare," Doran told several hundred Navy officers and invited guests gathered on Sierra 9 pier.

Sullivan, who assumed command in August of 2003, is retiring from the Navy after a 35-year career. Cassias is returning for his seventh assignment in Hawai'i and his fourth job with the submarine force staff.

Cassias' previous assignment was as commander of Submarine Group Ten, Submarine Group Two, and Navy Region Northeast.

Doran said through the past 20 months, Sullivan commanded the Pacific submarine force "superbly." The seven ballistic missile submarines under his command completed 26 "deterrence" patrols.

That was accomplished as two subs were transferred to shipyards for conversion to guided missile submarines; a ballistic missile submarine was transferred to the Pacific from the Atlantic; another sub was docked for nuclear reactor refueling and overhaul; and the USS San Francisco out of Guam smashed into an undersea mountain on Jan. 8, killing one sailor and injuring 60.

Silent Hammer, an experiment conducted in October off San Diego, demonstrated how special operations forces operating from a submarine, and supported by unmanned aerial vehicles, can conduct clandestine operations in shallow waters.

Pearl Harbor will become the home port for the third Virginia-class submarine being built, the USS Hawai'i. Six more attack submarines also could be moved to the Pacific, including two more for Hawai'i.