The U.S. is sending its most advanced amphibious transport dock ships as well as its newest mine countermeasure ships to Sasebo, Japan.

The moves, U.S. Navy officials says, demonstrate the U.S. commitment to the defense of Japan and the security and stability of the vital Asia-Pacific as the Pentagon continues its rebalancing of forces to that region.

The San Antonio-class amphibious transport dock ship LPD-20 USS Green Bay will join the U.S. 7th Fleet in February 2015. The vessel will replace the Austin-class LPD-9 USS Denver, which is the Navy’s oldest ship on active duty next to the USS Constitution, serving since 1968.

Green Bay is a member of the latest amphibious transport dock (LPD) class, Navy officials note, and represents a significant improvement in capability for the fleet. The ship is equipped with an advanced command-and-control suite; increased lift capacity with substantial increases in vehicle and cargo carrying capability; and advanced ship survivability features. The ship supports the rapid transfer of personnel and equipment via the landing craft and MV-22 Osprey tiltrotor aircraft, making the ship a critical element for amphibious ready groups and expeditionary strike groups.

Denver will prepare for decommissioning and transit to Pearl Harbor in the summer of 2014 for final decommissioning in September 2014.

The amphibious assault ship USS Peleliu (LHA 5), homeported in San Diego, will go to the U.S. 7th Fleet area of responsibility to mitigate the gap in amphibious presence until Green Bay’s arrival.

The Avenger-class mine countermeasure ships MCM-9 USS Pioneer and MCM-14 USS Chief will report to the U.S. 7th Fleet as part of the Forward Deployed Naval Forces (FDNF) in Sasebo in May 2014. The Pioneer will replace the mine countermeasure ship MCM-1 USS Avenger, and the Chief will replace MCM-2 USS Defender. The Avenger and the Defender have served in the the FDNF since 2009.

Pioneer and Chief represent a significant improvement in capability for the FDNF. Avenger and Defender will both prepare for decommissioning and eventually be heavy-lifted back to their homeport of San Diego in June 2014.

This hull swap is called an Overseas Force Structure Change and is part of the Navy’s long-range FDNF strategy to rotate newer and more capable units forward. Built by Peterson Builders Inc., in Sturgeon Bay, Wis., Avenger is the first of the Navy’s Avenger class of mine countermeasures ships.

Eventually, Navy mine countermine ships are slated to be replaced by Littoral Combat Ships.