SEOUL, South Korea (AP) — At first glance it seems like a blockbuster: North Korea has reportedly offered up its nukes for negotiation, an abrupt reversal from its repeated vows never to relinquish the "treasured sword" it sees as protection against constant U.S. "hostility."

Experts reading between the lines, however, believe the North may be falling back on a well-worn position when confronting the United States. Essentially: You want our nukes? Then give us credible security guarantees.

This has been seen in the past to mean the removal of the 28,500 U.S. troops stationed as a deterrent aga...