Despite strong international pressure, even from ally China, North Korea tested a third nuclear device Feb. 12, its most powerful to date, prompting an emergency session of the United Nations Security Council at which the action was unanimously condemned.
What's behind North Korea's latest move? Here are four brief points to know:
Why is this latest test by North Korea of such concern?
Experts say it indicates the country may be getting closer to being able to put a nuclear warhead on a missile. The test appeared to show an increase in North Korea's nuclear capability. In an English-language statement acknowledging the test, North Korea characterized the device as "a smaller and light A-bomb, unlike the previous ones." The nation also acted against the will of its primary ally and sponsor, China, calling into question China's ability to check its neighbor. China declared its "firm opposition" to the test.
The yield of the bomb was equivalent to 6,000 tons of TNT, or 6 kilotons. That's bigger than either previous test, in October 2006 (1 kiloton) and May 2009 (2 kilotons). The bombs dropped on Hiroshima and Nagasaki, Japan, were about 13 kilotons and 20 kilotons, respectively.
Why did North Korea do it?
"This is meant to get the attention of South Korea, the US, Japan, and – dare I say it – China," says Sung-Yoon Lee, assistant professor of Korean studies at Tufts University in Medford, Mass. "With leadership transitions going on in all those countries, this is a particularly appeasement-prone time. None of those countries want a foreign-policy crisis at the moment and will be more likely to resort to damage-control diplomacy."
The North is trying to persuade the world – and in particular the United States – that it is a full-fledged nuclear power that can threaten others as much as it is threatened by them. That Pyongyang chose the day of President Obama's address on the state of the Union on which to conduct its test indicates how much the test was meant as a message for the US, regional analysts say.
The test was also directed at an internal audience. Leader Kim Jong-un, in power for just a year, is still establishing his credentials, observers say, and a successful test adds to his prestige and legitimacy, thus strengthening internal security.
The true aims of North Korea, however, remain officially unstated, and therefore open to speculation.
What are the likely ramifications for North Korea?
It's likely to further isolate the Pyongyang regime. Analysts say that hopes for improved relations with the new governments in Washington, Seoul, Tokyo, or even Beijing are now on hold – at least for the time being. The test, in part a defiant response to sanctions, will probably result in even more sanctions.
It may be weeks before the United Nations Security Council comes up with a resolution whose measures could include anything from travel bans on officials involved in the North's weapons programs to even stricter inspections of North Korean vessels and financial sanctions, regional experts say. During that time all eyes will be on China to see how far Beijing, increasingly exasperated with its troublesome ally and neighbor, is willing to go to punish the North for its actions.
How much of a threat to the US is North Korea's nuclear program?
Outgoing US Secretary of Defense Leon Panetta told Pentagon workers recently that North Korea's missile and nuclear programs represent "a serious threat to the United States of America." But the prospect of North Korea being able to launch a nuclear-tipped missile at the US is not an immediate one. There is no evidence that Pyongyang has mastered the tough task of miniaturizing a nuclear warhead sufficiently to use on a ballistic missile (though Pyongyang claims that progress had been made in that direction in its latest test).
A 2012 display of missiles on portable launchers said to be intercontinental ballistic missiles were declared fakes by Western intelligence analysts, and indicated that North Korea was a long way from having a credible ICBM.
After 14 years of trying, North Korea did finally succeed in placing a satellite in orbit – briefly – in December. Its nuclear program began in 1989.