It has been decades since bombs fell and bullets flew on the Korean peninsula. Yet the United States, China, North Korea, and South Korea still technically are at war. The Korean War ended in an armistice, not a peace treaty.
The time is long overdue for the "combatants" to declare a state of peace.
Until now formally ending the war might have seemed premature. North Korea launched routine rhetorical fulminations and occasional violent attacks over the years. The North's conventional forces were essentially spring-loaded just north of the Demilitarized Zone, ready to resume combat. Furthermore, despite Pyongyang's sometimes pacific protestations, it didn't seem like the North Korean leadership actually wanted peace.