Under the new U.S. deployment arrangement in Japan, Marines who are serving in Okinawa as part of the 12th Marine Regiment, an artillery unit, will transform into a more mobile unit — the 12th Marine Littoral Regiment. The new configuration will allow them to more easily fan out to other islands along the coast when the need arises, U.S. officials said. The littoral regiment will have battalion-size units, about 2,000 troops total, and have long-range fire capabilities that can hit ships. Mr. Austin said the change will lead to a presence that is “more lethal, more agile, more capable.” The…