Before Christmas, a contingent of 105 U.S. Marines who would have been sent to Okinawa were redirected to a new base on the United States territory of Guam instead. The small reshuffling marked a major milestone: This was the first time the Marines cut their head count on Okinawa as part of a deal between Washington and Tokyo to shrink an oversized U.S. military presence on the Pacific island that dates back to World War II.

Under the agreement, 9,000 Marines — just under half the force currently on the island — are eventually supposed to leave. But their departure is already two decades behind the original schedule and may not happen for more than a decade to come, until construction of replacement bases is completed.

Their redeployment was agreed to in a deal signed 12 years ago, the result of negotiations and renegotiations going back to 1995, when three U.S. servicemen raped an Okinawan schoolgirl. That crime touched off mass protests that forced the United States and Japan to agree on shrinking the American bases, which were built after the United States stormed Okinawa during a bloody battle in 1945.