Total air defense is effectively impossible. In a major war, the West may have to make hard choices.

The West has strong air defense systems, but would still have to make choices about where to protect in a large-scale war. Sean Gallup/Getty Images Air defense is becoming harder than ever in modern war with drone and missile proliferation. It makes it effectively impossible to defend everything — even with substantial spending on defenses. In a major war, the West would have to make tough choices about what to protect. In a major armed conflict, even the most advanced militaries will not b...