On the eve of President Barack Obama's State of the Union address, North Korea sent him a pointed reminder with an underground test of a nuclear weapon that it intends to pose a significant national-security challenge.
North Korea's underground test of a nuclear bomb Tuesday was not just a big step toward that country's goal of building an offensive nuclear weapon but a shot across the bow of President Barack Obama.
In making the point that they are determined to become one of the world's handful of nuclear powers, the North Koreans have not just rattled America's cage but that of the United Nations, Japan and South Korea, not to mention longtime ally China.
It's hard to predict what comes next, although North Korea has indicated that it will continue tests on a bomb that could be delivered to the American mainland by missile.
Obama warned North Korea that nuclear tests "do not make North Korea more secure." But it would appear that North Korean leaders think that becoming a nuclear power not only enhances their national security but also is a crucial ingredient to achieving respect and economic concessions from other countries.
Of course, one cannot be certain about North Korea. It is not called the "hermit kingdom" for nothing. It remains perhaps the most bizarre example of a totalitarian communist government in world history, exceeding even the secrecy, paranoia and cult of personality that marked the Soviet Union under Stalin and the People's Republic of China under Mao.
North Korea is a desperately poor country that, apart from its military, can barely hold itself together.
Its people are starving and its economy is moribund, but the country's ruling military elite clings to power on the strength of political propaganda and ruthless suppression of dissent.
North Korea's poverty and brutality stand in stark contrast to the political freedom and economic prosperity enjoyed by South Korea. So stark are the differences, diplomats and academics have speculated for years that it's only a matter of time before North Korea's government collapses and the two countries merge into one, much as East and West Germany did after the collapse of the Soviet Union.
Indeed, the fear of impending collapse may well be what is motivating North Korea to build its own nuclear program and use it to secure the economic concessions it needs to survive.
So far, however, North Korea's saber rattling has resulted only in further hardship. Its already listless economy has been the subject of economic sanctions from the United States and other countries intended to persuade North Korea that pursuing nuclear weapons is not worth the economic price it is paying.
One key to bringing North Korea to heel, if that is possible, is the extent to which China is successful in changing North Korean behavior. A neighbor to North Korea, China's aid and support have been crucial to its survival. In return for that support, North Korea has proved to be a useful geographic buffer for China from the political and military influence of South Korea and the United States.
There are limits to the benefits China receives from that relationship, and North Korea's pursuit of nuclear weapons and constant provocations might persuade China to rethink its approach.
The best-case scenario is that there is a method to the apparent madness of North Korea, that it is truly a rational actor trying to give every appearance of being irrational. But that is just a theory, one undermined by the bizarre nature of North Korea.
In a world filled with trouble spots, North Korea stands near the top of the list and appears to be determined to achieve the title of No. 1 hot spot.