China's Challenge: As tensions elevate on the Korean peninsula, Pyongyang's patron deploys a weapon designed to sink the very ships we are sending to protect an ally. This does not bode well. The prospects that the Korean War, which ended in only an interminable armistice, may resume has become an increasingly real possibility in recent months. That its patron, China, without which North Korea would collapse of its own rot, now has deployed a missile designed to target and sink U.S. carrier battle groups adds a new and disturbing element to any confrontation in the region. Admiral Robert Willard, commander...