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Comment by verelo | Hacker News Reader

So I'm a little confused, what's all this talk about anti-missile systems? Are they even real or just seriously over-stated? If you look at where Hokkaido is I feel it's hard to believe that some protection system wouldn't activate when the missile lands on the eastern side if the island.

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Thinking more about it, perhaps it makes sense. If they know it's going to miss the area, why blow it up and give away information about your defence systems. I bet that is a risky and nail biting call to make...

Anti-missile defense systems on the ballistic scale are pretty much a 50/50 proposition. There's signs they may have been testing multiple re-entry vehicles as well, which makes it even more difficult.

But just because anti-missile systems weren't used here doesn't mean they don't exist. US/Japan could have decided the missile was probably headed for the Pacific and decided not to intercept. The location and capability of US anti-missile batteries would be strategically useful information for NK, so better to keep them quiet if you don't have to use them.

It depends very much on the type and speed of missile you're intercepting. For short-range rockets, the technology is pretty solid (Israel's Iron Dome has an excellent track record). For battlefield weapons and cruise missiles, it's OK (the effectiveness of the Patriot anti-missile system is hotly debated, but it seems to have a success rate of "more than 10% and less than 80%"). For things like ICBMs, we're really not even close.

The thing is, NK has one of the largest military in the world and can fire 200,000 or so rounds of mortars, tanks, rockets whatever to Seoul within 5 mins. A missile system can maybe defend 10,000 during that time? Just a back of the envelope calculation.

The anti-missile system being talked about recently is in South Korea, not Japan.

No, Japan is supposed to have some too.

Wonder why the did intercept, that has to have been a lively debate

It landed "Off the eastern coast of Hokkaido", which is a pretty ambiguous location. It might not have been very close to land, or on a trajectory that was particularly threatening.

NHK reports it landed about 1200km straight east of Hokkaido in the sea.

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