NK has been doing this for decades. Start some policy that angers the world and terrifies the South, ignore all diplomatic overtures until stuff starts to look really bad, then come to the table with an "historic" peace offering which leaves them in position to advance starting from the previous point when it looks like dire times again.
The leadership is interested only in preservation of the existing order. Every maneuver is directed towards that. They know they will lose the next war, but know that the damage to the South is not acceptable to any western nation. They don't want war, but need to stay in power. Concessions will be made, and in ten years they'll have nukes again.