China’s tough neighborhood has gotten just a little bit tougher for China, diplomatically and militarily, and Beijing ought to blame its own political blundering.

Consider South Korea and Vietnam, two of China’s more militarily capable neighbors. During the Vietnam War, South Korean soldiers fought Hanoi’s troops. Today, both countries regard that as very ancient history, and they increasingly act as de facto allies. This week, South Korea and Vietnam announced that they will strengthen bilateral defense cooperation and conduct a “strategic dialog” on defense issues. Defense cooperation includes senior officer training exchanges and defense industry collaboration. Shared senior officer training programs are a short policy step away from crafting shared defense plans.