North Korea's recent blast was tiny, but its commitment to nuclear weapons is long.
In July 1955, researchers from North Korea's Academy of Sciences traveled to Moscow to attend a conference on nuclear energy. Shortly thereafter, the Kim Il Sung regime began sending specialists to a new institute in Dubna, a city devoted to Soviet nuclear physics. Their mission: learn the basics of splitting the atom.
From that seed, a bomb may have grown. On Oct. 9 – more than a half century after that first delegation left Pyongyang – North Korea conducted a nuclear test in the northeastern region of Kilju.
The test was small, and possibly a failure. But US experts say that given the length of time the North Koreans have been at work, and the apparent importance of nuclear weapons to the country's leadership, they may now continue to test until they get it right.
They might not have labored five decades just to produce a scientific demonstration. At this point, they could be perfecting something else: a deliverable nuclear arsenal.
"My own view is that they are building a smaller weapon in line with a device that could fit on a ballistic missile," says David Albright, a physicist and president of the Institute for Science and International Security (ISIS) in Washington.
At the time of writing, North Korea had not conducted a second nuclear explosion. But US satellite imagery reportedly has revealed increased activity around several possible test sites.
"We're concerned about further action by the North Koreans, but further action by the North Koreans will only deepen its isolation, which is pretty deep right now," said Secretary of State Condoleezza Rice on Wednesday in Tokyo.
North Korean officials, for their part, did not rule out a second test. In a rare interview with a Western news organization, Ri Gun, director-general of the Foreign Ministry's American affairs bureau, told ABC News that another test would be "natural."
That is just what worries nuclear experts in the United States.
According to a statement issued by the office of John Negroponte, US director of national intelligence, the explosive yield of the Oct. 9 test was "less than a kiloton." It is possible that this relatively low yield was intentional, the result of a proof-of-principle design using minimal fissile material. But it is much more likely to indicate a test fizzle, say experts.