What is it that you don't understand here? Are you un-able to understand an insane dictator? Do you think the USA sends over that much artillery for free? No it costs money and a lot of it. S-Korea and Japan are probably scared that Kim Jun Nam is going to use the weapons as soon as he can. Its not like he just fired off several missiles at Japan a month ago and a few of them almost hit its main land. (that was sarcasm because he did)

If during the cold war Russia had fired off a couple missiles at the US and they landed just off shore of California and within the US's sovereign waters. Then there would have been war.