San Diego will replace USS Green Bay (LPD 20), also a San Antonio-class amphibious transport dock ship, which has been forward deployed to Sasebo for a decade. Green Bay will return to the United States at its new homeport of San Diego.

The forward presence of San Diego supports the United States’ commitment to the defense of Japan, enhances the national security of the United States and improves its ability to protect strategic interests. San Diego will directly support the Defense Strategic Guidance to posture the most capable units forward in the Indo-Pacific Region.

"USS San Diego is prepared for this move. Being forward deployed will be very rewarding for the crew and families. We appreciate all the support and fond memories of the City of San Diego, but it's time for the city's namesake USS San Diego to lead the charge. America is counting on us to deter aggression, defend our national security interests, and preserve our way of life," said Capt. David Walton, San Diego commanding officer.

San Diego was commissioned May 19, 2012, and has been stationed in San Diego for 12 years. The ship’s motto is “Semper Vigilans,” or “Always Vigilant.” Its crest, adapted from the City of San Diego’s coat of arms, recalls the city’s origin as a mission settlement. The mission bell has been replaced with a ship’s bell, acknowledging the city’s long-standing connection to the maritime industry and the U.S. Navy. The palm wreath signifies honor and victory.

Maintaining an FDNF capability with the most advanced ships supports the United States’ commitment to the defense of Japan and the security and stability of the vital Indo-Pacific region.