Learning from South Korea's predicament

America's security commitments to its allies and partners are no longer credible

If you think you have problems, think about South Korea. Your next door neighbour, North Korea, is developing nuclear warheads that it can put on a missile, which can reach any part of your country. It already has enough artillery and conventional missiles that can kill hundreds of thousands of people in your capital city within hours. It regularly threatens to use them.

Now you could install a missile defence to protect your cities, but your other, giant next-door neighbour, China, doesn’t want you to do that and has long discouraged you from installing one. This missile defence shield — called