Did North Korea Detonate a Hydrogen Bomb? Here’s What We Know
North Korea’s
claim that it set off a hydrogen bomb on Wednesday — in what would be
the fourth time it has tested a nuclear weapon since 2006 — has stirred
concerns among governments around the world. Below is a brief primer on
some of the central issues at stake.
Q. What, precisely, did North Korea announce?
A. The North’s government said that it had detonated a hydrogen bomb — its first — at 10 a.m. on Wednesday.
“This
test is a measure for self-defense the D.P.R.K. has taken to firmly
protect the sovereignty of the country and the vital right of the nation
from the ever-growing nuclear threat and blackmail by the U.S.-led
hostile forces and to reliably safeguard the peace on the Korean
Peninsula and regional security,” it said, referring to the North’s
formal name, the Democratic People’s Republic of Korea.
Q. How is a hydrogen bomb different from an atomic bomb?
A.
A hydrogen bomb, also known as a thermonuclear bomb, combines hydrogen
isotopes under extremely high temperatures to form helium, in a process
known as nuclear fusion. It is more powerful than a conventional atomic
weapon: It uses the energy released from the combination of two light
atomic nuclei, while an atomic bomb uses the energy released when a
heavy atomic nucleus splits, a process known as nuclear fission.
American scientists developed the hydrogen bomb, which was first tested
in 1952.
Q. How can North Korea’s claim be verified?
A. Governments and scientists are working to see if the claim is true.
The
United States Geological Survey reported that it detected a
magnitude-5.1 seismic event in the northeastern part of North Korea,
where the test is said to have occurred — roughly similar to what
happened in 2013, when North Korea tested an atomic bomb. But a South
Korean lawmaker, Lee Cheol-woo, said that his country’s intelligence
service estimated the event triggered an explosive yield of six kilotons
and a magnitude-4.8 event — smaller than the 7.9 kilotons and magnitude
4.9 reported after the 2013 test.
A
successful hydrogen bomb test would typically have an explosive yield
of hundreds of kilotons — or tens of kilotons, for a failed test — Mr.
Lee said.
Q. What if it was not a hydrogen bomb?
A. When Kim Jong-un,
the North’s leader, announced in December that his country had finally
developed the technology to build a thermonuclear weapon, experts were
skeptical. Some said that North Korea might be preparing to test a
“boosted-fission weapon,” more powerful than a traditional atomic bomb.
Designers can easily increase the destructive power of an atomic bomb by
putting at its core a small amount of tritium, a radioactive form of
hydrogen. The Yonhap News Agency of South Korea reported that the
government in Seoul was leaning toward the theory of a boosted-fission
weapon, “one level away from a hydrogen bomb.”
Q. How many times has North Korea detonated a nuclear weapon?
A. This appears to be the fourth time. North Korea conducted underground nuclear tests on Oct. 9, 2006; May 25, 2009; and Feb. 12, 2013.
Q. What might North Korea be trying to accomplish with its threats?
A. In
the past, United States administrations and South Korean governments
managed to tamp down periodic heightened tensions with North Korea by
offering concessions, including much-needed aid, in return for the
North’s promising to end its nuclear weapons
programs. Many analysts believe that North Korea is again seeking aid
and other concessions, while some suggest that it merely wants to be
recognized as a nuclear state, like Pakistan.
Still
others suggest that the North genuinely fears an attack by the United
States or South Korea and views the warnings as deterrence. Highlighting
a perceived threat from abroad is also a favorite tool the North Korean
government uses to ensure internal cohesion in an impoverished country
that has experienced enormous privation, including devastating famine
and continuing pervasive hunger.
Q. Could North Korea attack the United States?
A.
Maybe. In 2012, North Korea launched a rocket that put its first
satellite into orbit — raising the possibility of intercontinental
ballistic missiles that could reach North America. The United Nations
Security Council condemned the launching as a violation of several
Security Council resolutions and tightened sanctions against it.
Q. How might the United States, China, Japan and South Korea respond to a missile test or an attack?
A. If
a missile attack went into the water, even if it passed over Japan, the
two countries could ignore it. But if it headed for land, the United
States would probably use its missile interception technology, including
on Aegis-equipped ships off the Korean coast. If there were to be a
more direct attack, like the torpedo that sank a South Korean warship in
2010, it is likely that both the United States and South Korea would
respond. China would be less likely to take action.
Q. What was the global response to previous North Korean rocket launchings?
A.
As the North’s missile technology has become more sophisticated, the
launching of longer-range missiles has evoked more international
concern.
In
1998, when the North launched a Taepodong that flew over Japan, Japan
temporarily cut off its contribution toward a North Korean energy
project. But in July 2006, when the North launched another long-range
missile, various countries began imposing sanctions, while the Security
Council began adding to economic sanctions.
In
April 2009, when the North’s efforts to launch a three-stage Unha-2
rocket failed, the Security Council said it would strengthen punitive
measures. It did so after the North conducted a nuclear test the next
month.
In April 2012, the United States canceled planned food aid
when the North tried to launch a more advanced missile, the Unha-3.
That launching failed, but another in December succeeded in lifting a
small satellite into orbit. The Security Council tightened sanctions yet
again. After the North’s nuclear test in February 2012, China, the
North’s longtime protector, participated in writing painful new
sanctions aimed at North Korean banking, trade and travel.
Q. What is the Obama administration’s policy on North Korea?
A. The
Obama administration adopted a policy of “strategic patience” in 2009,
under which direct negotiations or offers of aid to Pyongyang are
withheld unless the North Korea leadership shows “positive, constructive
behavior” and willingness to negotiate over the dismantling of its
nuclear weapons program.
The
policy is a response to the American belief that the United States had
unwisely offered aid, often in the wake of Pyongyang’s provocations, or
struck agreements with the North on which the North later reneged.
Strategic patience, in the words of Robert M. Gates, the former defense
secretary, grew out of a desire not “to buy the same horse twice.”
Critics
say that while the policy has allowed the United States to weather
multiple rounds of belligerence by Kim Jong-il and his son, Kim Jong-un,
without making concessions, it has done little to curb the development
of North Korea’s nuclear weapons program.
Q. What sanctions are currently in place?
A.
The Security Council has passed four resolutions since 2006 aimed at
penalizing North Korea for its nuclear weapons program. In addition, the
United States, which remains in a technical state of war with North
Korea, has imposed its own regimen of strict economic sanctions. The
combined effects have severely squeezed, but not crippled, North Korea’s
economy. The United Nations has prohibited the North from conducting
nuclear tests or launching ballistic missiles, requested that it abandon
all future efforts to pursue nuclear weapons and urged it to return to
negotiations with China, Japan, Russia, South Korea and the United
States, the so-called six-party talks.
The
resolutions have also imposed embargoes on large-scale arms,
weapons-related research and development materials, and luxury goods;
banned many types of financial transactions including transfers of cash;
placed new restrictions on diplomats; and created monitoring mechanisms
for enforcement.
The American sanctions
freeze all North Korean property interests in the United States, ban
most imports of goods and services from the North, and prohibit American
dealings with any names on a blacklist of North Korean businesses and
individuals suspected of illicit activities including money laundering,
counterfeiting, currency smuggling and narcotics trafficking.
Nothing
in the American sanctions prohibits American travel to North Korea or
the export of food and other types of humanitarian aid, although there
are some restrictions.
The
sanctions leave room for considerable trade in many types of goods and
services. China, which supplies much of North Korea’s basic needs, is
not in any violation of the United Nations resolutions.
Q. How is the South Korean government responding to the North’s threats?
A. President
Park Geun-hye, who took office in 2013, is the daughter of a former
president who ran South Korea as a dictator during the Cold War. She
once promised that if the North mounted a nuclear attack, its government
would be “erased from the earth.” She has largely held a firm line on
North Korea, after a more conciliatory stance in the 1990s.
From
1998 to 2008, the South pursued a “sunshine policy” of reconciliation
and economic cooperation that sent billions of dollars in business
investments, goods and humanitarian aid to the North. Ms. Park’s
immediate predecessor, Lee Myung-bak, said the North would need to give
up its nuclear weapons to receive any more aid. But he was criticized
for what many saw as a weak response after the North shelled a South
Korean island in 2010, killing four people.
Q. Why
hasn’t China stopped North Korea from its campaign of threats? Is there
any other country that has enough influence on North Korea to stop it?
A.
China, the North’s patron, has long feared that a collapse of the North
Korean government could lead to a unified Korea allied with the United
States.
China
helped write and backed the most recent round of United Nations
sanctions, but it has been loath to push the North too hard. Its
patience with the North may be running out, but even China may have only
limited information about the machinations within the Pyongyang
government.
Q. Why are relations so bad between North and South Korea?
A. After the United States and the Soviet Union divided the Korean Peninsula at the end of World War II
in 1945, they helped install rival governments in Seoul and Pyongyang.
Each asserted claims to the whole of Korea. The two fought the 1950-53
Korean War, which ended not in a peace treaty but a truce. Mutual
mistrust runs deep, although there have been intermittent attempts at
political reconciliation and economic cooperation.
Q. How did the North get nuclear weapons?
A.
The project started under Kim Il-sung, the country’s founder and the
grandfather of the current leader. Mr. Kim knew that Gen. Douglas
MacArthur wanted Washington to allow the use of nuclear weapons against
Chinese and North Korean troops during the Korean War.
By
the 1980s, American intelligence satellites were watching the nuclear
complex at Yongbyon come together. Relations between the United States
and the North grew especially tense over the issue in 1994, and some in
the White House feared a war could break out. A pact was eventually
hammered out that year, the Agreed Framework, but it fell apart in 2002,
during the George W. Bush administration, partly over allegations the
North was cheating on its agreements and developing another path to a
bomb. In 2006, the North conducted its first nuclear test, a partial
fizzle. But the subsequent tests were more successful.
