As for North Korea "coming to heel"...the mountain that they were testing their nuclear weapons collapsed, pretty sure that had A LOT to do with their stopping nuclear testing. Plus, Kim Jong Un has stated that no more tests are needed. But, we've heard this before. Let's take a trip down memory lane shall we.
In 1985, North Korea signed the UN Nuclear Non-proliferation Treaty.
In 1992, North Korea signed a treaty with South Korea whereby both promised not to pursue nuclear weapons.
In 1994, North Korea signed a treaty with the U.S. promising to freeze and dismantle its nuclear program in exchange for aid (millions of people starved to death in North Korea in the 1990's as the result of a horrendous famine). It was discovered in 2002 that North Korea had been operating a secret nuclear program in violation of the 1994 treaty.
In 2005, following the Six Party Talks, North Korea formally agreed to give up its nuclear program in exchange for energy aid and new trade oppoetunities with the other 5 members of the talks (China, Russia, Japan, South Korea, and the U.S.); North Korea successfully tests its first nuclear warhead in 2006, violating the terms of this agreement. Six Party talks continue to try to resolve the situation until 2008, when they finally break down.
In 2010, North Korea issued a statement saying it would be party to non-proliferation and disarmament "on equal footing with other nuclear weapon states."
In 2011, Kim Jong Il agrees in negotiations with Dmitry Medvedev (Russia) to halt the nuclear weapons program; there are talks about bringing back the Six Party negotiations.
In 2012, North Korea agreed to temporarily stop testing and operation of a Uranium enrichment facility in exchange for food aid from the U.S. The U.S. withdrew food aid when it discovered North Korea was still operating these facilities.