YOKOSUKA NAVAL BASE, Japan -- Incoming first-term sailors assigned to sea duty in Japan, Guam or Spain will now be required to serve four years at their new commands, the Navy announced Tuesday.

The change -- which affects first-term sailors who receive orders issued May 1 or later -- aims to "improve readiness and reduce turnover of our Forward Deployed Naval Force," the service said.

Sailors now stationed in the affected countries will continue to serve out their two- or three-year deployments, the Navy said.

Affected sailors whose dependents are denied command sponsorship will be issued a maximum of two years unaccompanied orders, the service said. In February, the Navy began allowing accompanied tours for E3 and below. Those without dependents receive the full four years.

Vice Adm. Robert Burke, who serves as chief of Naval Personnel and deputy chief of Naval Operations, first told sailors of the Navy's intent to extend tour lengths during a January town-hall meeting in Yokosuka.

"A sailor gets [to Japan and] they're taking 12 to 18 [months] to learn their training and then maybe doing their job for a short period of time before it's time for them to move again," Burke said in January. "That puts the commands in a state of continuously having to train up their people and not having a seasoned, experienced crew that can train up the new junior folks."

Those who were assigned to sea duty in Japan, Guam or Spain before May 1 will be eligible for incentives to extend their tours. In February, the Navy offered to waive any remaining sea time on tour lengths and guarantee shore duty for the next assigned tour if sailors opted to extend to four years.

Those extending tours by a year or more are given preferential consideration for billets announced in Career Management System/Interactive Detailing, a web-based system used to view and apply for jobs.

"Our goal is to reward those sailors who volunteer to extend to meet the demands from the fleet," Rear Adm. John Meier, director of the Career Management Department for the Navy Personnel Command, said in February.

Post-May 1 first-term sailors are not eligible for the extension incentives, but will have any remaining prescribed sea tour from their first sea duty tour waived. They will become eligible for the incentives after completing their first tour.