Why allies may prefer missile defense to new nuclear arsenals

Would states such as Japan, Sweden, or South Korea answer the 2022 security crisis by acquiring nuclear weapons?

Japan would probably prefer ballistic-missile defense, Sweden could combine stronger defenses with NATO membership, and South Korea might reconsider a nuclear program despite the high acquisition cost.

This speculation is tied to the first days of Russia's invasion of Ukraine. The political legacy of Hiroshima and Nagasaki made ballistic-missile defense a more likely Japanese choice than an independent nuclear arsenal. Sweden could seek collective deterrence through stronger defenses and NATO membership without bearing the full burden of a national arsenal. Becoming a nuclear power would be costly even if maintaining an established force were more manageable, while South Korea might reconsider earlier work.