While political and military analysts sound pretty confident that North Korean leader Kim Jong Un's threats are just bluster, you can't get around the fact that the region encompassing the Korean peninsula is one of the most heavily militarized places on Earth, home to three of the world's six-largest militaries.

If the unthinkable were to happen, how would it play out?

Leon Panetta, who stepped down as President Barack Obama's defense secretary in February, warned this week in an interview with CNBC that "we don't have as much insight as we should with regards to the inner workings of what happens in North Korea."

But based on declassified U.S. and U.N. assessments and independent analyses by military scholars, we can make some educated guesses:

How would North Korea attack?
Probably with a massive ground assault backed by artillery fire. That's because North Korea's standing military, according to the best U.S. and U.N. intelligence assessments, is the fourth largest in the world, at 1.1 million members. South Korea's, by contrast, is about 690,000 strong.

Library of Congress Federal Research Division

That ratio — a manpower superiority of roughly 3-to-2 for the North — is remarkably consistent across calculations of the countries' weaponry, too. By about the same proportion, the North has more tanks, more artillery, more planes, more ships, more missiles. 

In a 2008 report commissioned by the U.S. Joint Chiefs of Staff, the Federal Research Division of the Library of Congress depicted North Korea as, in essence, one giant military installation (see map at right).

How would South Korea respond?
By being smarter and nimbler.

Much of the North's equipment is seriously outdated, going back to its alliance with the former Soviet Union during the Cold War. 

The South's weaponry is less extensive but far more advanced, thanks to modern equipment provided by the U.S. 

"Overall, South Korea's armed forces have become one of the world's more capable militaries and present a formidable forward defense against any possible attack by North Korea," the British-based International Institute for Strategic Studies concluded in 2011.

All of that presumes that North Korean troops could make it into the South in the first place. To get there, they would have to go through about 28,000 U.S. troops stationed along the Demilitarized Zone separating the two countries, supported by about 40,000 more just a short hop away in Japan and on a large military base in Guam.

Doesn't Kim have China to back him up?
In theory, yes, and that's no small matter. 

China's 2.3-million-strong miitary is the world's biggest, outpacing the U.S.'s by almost 40 percent. In its annual report to Congress last year, the U.S. Defense Department didn't estimate how many Chinese forces might be based in North Korea, but it did outline the massive array of forces China is believed to have inside its own borders facing the Korean peninsula:

The map at left depicts China's naval buildup around the Korean peninsula. The map at right details army deployments. Click each map for its full-size version.

But it's not clear that China has the stomach for a fight. Beijing has signaled its displeasure with the North's recent provocations — just last month, it voted for a U.N. resolution to impose sanctions in response to North Korea's announcement of a nuclear test on Feb. 12.

P.J. Crowley, an assistant secretary of state during Obama's first term, told NBC News that Kim's erratic behavior has created major "frustration" in Beijing, which he said "does not want to see an implosion of North Korea."

The U.S., on the other hand, has made it clear that it will defend South Korea. To drive home the point, it sent F-22 stealth fighter jets to South Korea as part of military exercises in a show of force Sunday. And it has sent two warships to the western Pacific to watch for missiles and will soon send an advanced anti-ballistic missile system to its base on Guam, defense officials said.

Military and political analysts say China doesn't want a showdown over the Koreas because then the superpowers' nuclear arsenals become a factor. The U.S. said in an unclassified 2010 report (.pdf) that its stockpile was about 5,100 warheads — more than 20 times that of China, which the Bulletin of the Atomic Scientists estimated in 2011 at 240.

How long could South Korea hold out?
Much longer than the North.

To put it bluntly — as the CIA did in an economic assessment last month — North Korea is a mess internally. Industrial and power output have receded to pre-1990 levels, while frequent crop failures since a devastating famine in 1995 have compounded food shortages that have fueled chronic malnutrition. All that's keeping its people afloat are international food aid deliveries, mainly from China, which would almost certainly be disrupted or cut off in a war.

South Korea, in sharp contrast, boasts a high-tech industrialized economy — one of the 20 biggest in the world, the CIA reported. It has numerous trading partners worldwide to keep it fed and supplied. And because its communications and transportation systems are among the best in the world, it would be much better placed to coordinate civil defense and to move people and material out of harm's way.

So if a traditional assault is unwinnable, what are Kim's options?
Very scary ones.

The Center for International Studies and Research, a nonpartisan French research agency, calculated in October (.pdf) that the North can deploy "a full array of what are typically described as weapons of mass destruction" — one of the biggest chemical and biological stockpiles in the world at 2,500 to 5,000 metric tons, mostly tabun (a nerve agent) and mustard gas.

In a technically secret process, South Korea is believed to have told the Organization for the Prohibition of Chemical Weapons that it had destroyed its chemical weapons in 2008.

And then there are North Korea's own nuclear weapons — the real wild card in the deck.

U.S. officials and other researchers say North Korea may already have a few dozen warheads that could be fitted atop its vast fleet of ballistic missiles. They're fully capable of hitting targets in Japan, South Korea or elsewhere in the northern Pacific, the officials said.

Kim may be bluffing, as his father and grandfather did before him. But those weapons mean he must always be taken seriously.

Mission No. 1, Crowley said, is "figure out a way to denuclearize North Korea."

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Reuters file

A DigitalGlobe Satellite image shows construction at the North Korea's Yongbyon Nuclear complex on Nov. 2010.

SEOUL - North Korea will restart all nuclear facilities including its shuttered Yongbyon nuclear reactor, its official KCNA news service said on Tuesday.

It will rebuild and restart nuclear facilities including its mothballed uranium enrichment facility and the 5 MW Yongbyon reactor which it closed in 2007, KCNA quoted a spokesman at North Korea's atomic energy agency as saying.

It said the nuclear facilities would be used for both electricity and military uses.

Earlier, North Korea's leader appeared to tamp down hostile rhetoric that had threatened impending war with the United States and South Korea in a key speech published Tuesday that implied the isolated country was shifting its focus to development.

Pyongyang has launched relentless verbal attacks and threats against the United States and South Korea since new U.N. sanctions punishing it for its February nuclear test were adopted and during military drills by the South and U.S. forces.

But the speech delivered on Sunday by Kim Jong-Un focused on how nuclear capability supported economic development although it accused the United States of seeking to drag North Korea into an arms race in a bid to hinder its economic improvement.

"It is on the basis of a strong nuclear strength that peace and prosperity can exist and so can the happiness of people's lives," Kim said in the speech delivered to the central committee meeting of the ruling Workers Party of Korea and published in full on Tuesday.

Threats from North Korea have prompted the United States to beef up its forces on the peninsula and station a warship off the Korean peninsula overnight.

US Navy shifts destroyer in wake of North Korea missile threats

North Korea had cut off hotlines between it, the United States, South Korea and the United Nations and threatened to close a joint economic zone it runs with the South. It put its missile forces on full alert and threatened U.S. bases in the Pacific and on the mainland.

The North has promised its citizens that it would become a strong and prosperous nation and is moving towards celebrations of the April 15 birthday of its founder Kim Il-sung, the grandfather of the current leader.

"The fact that this was made at the Party central committee meeting, which is the highest policy setting organ, indicates an attempt to highlight economic problems and shift the focus from security to the economy," said Yang Moo-jin of University of North Korean Studies in Seoul.

The fortress island fixed in North Korea's sights

The 30-year old Kim, who took office in December 2011, said that no nuclear state had been invaded in modern history and that "the greater the nuclear attack capability, the greater the strength of the deterrent against an invasion."

"Our nuclear strength is a reliable war deterrent and a guarantee to protect our sovereignty," he said. 

This story was originally published on Tue Apr 2, 2013 1:38 AM EDT

Kcna Via Kns / AFP - Getty Images

A North Korean military spokesman announcing the end of the armistice that ended the Korean War in 1953.

South Korea's military said it will strike back at North Korea and target its top leadership if Pyongyang launches a threatened attack.

A top North Korea general, in a rare appearance on state television on Tuesday, threatened military action against the U.S. and South Korea because of military drills between the two western allies countries that began March 1.

Tensions have ratcheted higher across the Korean peninsula since the North, under youthful leader Kim Jong Un who took office just over a year ago after the death of his father, launched a long-range rocket last December.

Slideshow: North Korea's young leader, Kim Jong Un

The youngest son of Kim Jong Il succeeded his late father in 2011, becoming the third member of his family to rule the unpredictable and reclusive communist state.

Launch slideshow

He followed this with a third nuclear test on February 12, triggering the prospect of more U.N. sanctions that are due to be formally announced on Thursday after the United States and China, the North's one major diplomatic ally, struck a deal to punish Pyongyang.

At the same time, North Korea has stepped up its military threats against South Korea and the United States, prompting the terse warning from Seoul on Wednesday that it would not stand idly by if its territory was attacked.

"We have all preparations in place for strong and decisive punishment, not only against the source of the aggression and its support forces but also the commanding element," Major General Kim Yong-hyun of the South Korean army told a press conference.

North Korea's bellicose rhetoric rarely goes beyond that, although in 2010 it sank a South Korean naval vessel, killing 46 sailors and in the same year shelled a South Korean island, killing civilians.

South Korea's new President Park Geun-hye had pledged to engage with the North if it dropped its nuclear plans but now faces the prospect of a hostile challenge early in her 5-year term.

The proposed fresh sanctions would explicitly ban the sale to Pyongyang of items coveted by North Korea's ruling elite, such as yachts and racing cars, a U.N. Security Council diplomat said on condition of anonymity.

In 2009, Italian authorities blocked the sale of two yachts worth more than $10 million that they believed were headed for Kim Jong Il, the current Kim's father, who enjoyed copious amounts of luxury brandy and fresh sushi in a country where a third of the population is malnourished.

The new sanctions will target North Korea's financial transactions, which often involve using cash couriers that make them hard to trace, and its criminal activities such as drugs and counterfeiting.

North Korea was slapped with sanctions in 2006 that banned the import of a range of luxury goods from jet skis to Harleys following its first nuclear test in a bid to hit the high-life of the Kim family and its hangers-on.

The impoverished country, whose economy is smaller than it was 20 years ago, has been subject to sanctions of some kind from the United States for almost all of its existence and since 2006 has seen U.N. sanctions imposed for its long range rocket and nuclear tests.

Despite the sanctions Pyongyang now has a nuclear stockpile sufficient for around half a dozen warheads, has made substantial progress in developing a long-range missile and is working towards miniaturizing a nuclear warhead for an intercontinental ballistic missile.

China has backed all rounds of sanctions and fell into line with the latest move in the Security Council, risking relations with its prickly ally.

About 200,000 Korean troops and 10,000 U.S. forces are expected to be mobilized for their "Foal Eagle" exercise, under the Combined Forces Command, which goes until the end of April. Separate computer-simulated drills called "Key Resolve" start on March 11.

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Updated at 3:50 p.m. ET: The Rev. Sun Myung Moon, the self-proclaimed messiah who turned his Unification Church into a worldwide religious movement and befriended North Korean leaders as well as U.S. presidents, has died, church officials said Monday. He was 92.

Moon died Monday at a church-owned hospital near his home in Gapyeong, northeast of Seoul, two weeks after being hospitalized with pneumonia, Unification Church spokesman Ahn Ho-yeul told The Associated Press. Moon's wife and children were at his side, Ahn said.   

Church officials planned to meet later Monday to discuss mourning and funeral arrangements. The church will likely hold a 13-day mourning period and start accepting mourners at its nearby religious center on Wednesday, Ahn said.

Moon founded his Bible-based religion in Seoul in 1954, a year after the Korean War ended, saying Jesus Christ personally called on him to complete his work.  

The church gained fame -- and notoriety -- in the 1970s and 1980s for holding mass weddings of thousands of followers, often from different countries, whom Moon matched up in a bid to build a multicultural religious world. His followers were derisively referred to by critics as as "Moonies."

The church was accused of using devious recruitment tactics and duping followers out of money; parents of followers in the United States and elsewhere expressed worries that their children were brainwashed into joining. The church responded by saying that many other new religious movements faced similar accusations in their early stages.   

In later years, the church adopted a lower profile and focused on building a business empire that included the Washington Times newspaper, the New Yorker Hotel in Manhattan, Bridgeport University in Connecticut, as well as a hotel and a fledgling automaker in North Korea. It acquired a ski resort, a professional soccer team and other businesses in South Korea, and a seafood distribution firm that supplies sushi to Japanese restaurants across the U.S.   

“Words cannot convey my heart at this time,” said Thomas P. McDevitt, president of The Washington Times. “Rev. Sun Myung Moon has long loved America, and he believed in the need for a powerful free press to convey accurate information and moral values to people in a free world. The Washington Times stands as a tangible expression of those two loves.”

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“As controversial as Rev. Moon was in the United States, I got to know him as a man whose heart was focused on bringing together people of different faiths to bridge divides. His call on people of faith to serve others is an important legacy,” Neil Bush, chairman of Points of Light and son of President George H.W. Bush, was quoted as saying by The Times.

The Unification Church claims millions of members worldwide, though church defectors and other critics say the figure is no more than 100,000.   

In 2009, Moon married 45,000 people in simultaneous ceremonies worldwide in his first large-scale mass wedding in years. Some were newlyweds and others reaffirmed past vows. He married an additional 7,000 couples in South Korea in February 2010. The ceremonies attracted media coverage but little of the controversy that dogged the church in earlier decades.   

Lee Jae Won / Reuters

The Rev. Reverend Sun Myung Moon and his wife, Hak Ja Han, attend a mass wedding ceremony of the Unification Church in Gapyeong, South Korea, March 24.

Born in 1920 in what is today North Korea, Moon said he was 16 when Jesus Christ called upon him to complete his unfinished work. While preaching the gospel in North Korea in the years after the country was divided into the communist-backed North and U.S.-allied South, Moon was imprisoned there in the late 1940s for allegedly spying for South Korea -- a charge Moon disputed.   

He quickly drew young followers with his conservative, family-oriented value system and unusual interpretation of the Bible. He conducted his first mass wedding in Seoul in the early 1960s.   

The "blessing ceremonies" grew in scale over the next two decades, with a 1982 wedding at Madison Square Garden in New York -- the first outside South Korea -- drawing thousands of participants.   

"International and intercultural marriages are the quickest way to bring about an ideal world of peace," Moon said in a 2009 autobiography titled "As a Peace-Loving Global Citizen."

"People should marry across national and cultural boundaries with people from countries they consider to be their enemies so that the world of peace can come that much more quickly."   

Moon began rebuilding his relationship with North Korea in 1991, when he met the country's founder Kim Il Sung in the eastern industrial city of Hamhung.   

Moon said in his autobiography that he asked Kim to give up his nuclear ambitions, and that Kim responded that his atomic program was for peaceful purposes and he had no intention to use it to "kill my own people."   

"The two of us were able to communicate well about our shared hobbies of hunting and fishing. At one point, we each felt we had so much to say to the other that we just started talking like old friends meeting after a long separation," Moon wrote.   

He added that he heard Kim tell his son: "After I die, if there are things to discuss pertaining to North-South relations, you must always seek the advice of President Moon."   

When Kim Il Sung died in 1994, Moon sent a condolence delegation to North Korea, drawing criticism from conservatives at home. Kim's son and successor, Kim Jong Il, sent roses, prized wild ginseng, Rolex watches and other gifts to Moon on his birthday each year. Kim Jong Il died late last year and was succeeded by his son Kim Jong Un. Moon sent a delegation to pay its respects during the mourning period for Kim Jong Il.   

Moon also developed good relationships with conservative American leaders, including former Presidents Richard Nixon, Ronald Reagan and George H.W. Bush. Still, he served 13 months at a U.S. federal prison in 1984-1985 for tax evasion. The church says the U.S. government persecuted Moon because of his growing influence and popularity with young people in the United States, his home for more than 30 years.   

As he grew older, Moon quietly handed over day-to-day control of his multibillion-dollar religious and business empire, which included dozens of companies ranging from hospitals and universities to a ballet troupe, to his children.   

His youngest son, the Rev. Hyung-jin Moon, was named the church's top religious director in April 2008. Other sons and daughters were put in charge of the church's business and charitable activities in South Korea and abroad.   After ending a first marriage, Moon remarried a South Korean, Hak Ja Han Moon, in 1960. She often was at Moon's side for the mass weddings.   

The youngest son told The Associated Press in a February 2010 interview that Moon's offspring do not see themselves as his successors.   

"Our role is not inheriting that messianic role," he said. "Our role is more of the apostles, where we share ... where we become the bridge between understanding what kind of lives (our) two parents have lived."   

Moon is survived by his second wife and 10 children.

NBC News staff and The Associated Press contributed to this report.

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Australian Customs Service

Japan's whaling fleet already takes minke whales, like this mother and calf, and South Korea wants to do so as well.

When it comes to whaling, South Korea wants what Japan has: a loophole to hunt. Technically, the hunt would be for scientific research, but in reality it would eliminate competition for fishermen complaining about dwindling catches.

The U.S. on Thursday joined the list of nations opposing the move made Wednesday at the International Whaling Commission meeting in Panama.

In its opening statement, the South Korean delegation said the nation plans to use the same loophole in the international ban on whaling that Japan has been using to sustain its whaling fleet and domestic demand for whale meat.

That loophole allows a nation to sell for consumption any whales killed for research into whale biology or population dynamics. 

South Korean fishermen "are experiencing disturbances in their fishing activities due to frequent occurrences of cetaceans in their fishing grounds and an increasing number of minke whales are eating away large amount of fish stocks," the delegation stated, adding that South Korea, too, had a whaling fleet and market for whale meat before the 1986 ban.

The U.S. delegation responded Thursday via Twitter. "US believes lethal scientific whaling is unnecessary," it tweeted.

Conservationists, for their part, said overfishing, not competition from whales, is responsible for depleted fish stocks around the world.

Moreover, the minke whales being targeted by South Korea are considered endangered, the World Wildlife Fund said.

"The resumption of whaling by Korea after a quarter of a century would be a huge step back," said Wendy Elliott, who's leading the WWF delegation at the Panama meeting.

"Korea already sells meat from whales caught in fishing gear, and we believe this move is a thinly veiled attempt by Korea to conduct commercial whaling under the guise of scientific research, similar to hunts conducted by Japan in the Southern Ocean whale sanctuary," she added.

While it doesn't need specific permission to start "scientific whaling," South Korea said it had made a formal proposal to the commission's scientific committee.

That group could take a year or so to come up with its advice for South Korea, which is not bound by the recommendations.

Former Australian Environment Minister Ian Campbell, who is now on the board of the anti-whaling group Sea Shepherd, said the organization would "have to get organized to go out to the oceans and save the whales off South Korea," Reuters reported. 

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A Korean Airlines Boeing 777 sits on the tarmac of Comox Airport after being diverted from Vancouver International Airport due to a bomb threat.

Updated at 5:43 a.m. ET: Two U.S. F-15s were scrambled to escort a Korean Air passenger jet to a Canadian military base Tuesday after the carrier's call center received a "credible bomb threat," NBC News reported. The aircraft later made an emergency landing.

Korean Air flight 72, which was en route from Vancouver to South Korean capital Seoul, diverted to the Comox base on Vancouver Island in British Columbia, the airline said.

"The (Korean Air) U.S. call center received a call that there was a threat on board the aircraft," Korean Air said in a statement. The threat was received about 25 minutes after the flight took off, The Associated Press reported.

NBC News reported that Canadian authorities had requested U.S. assistance to escort the flight back to Canada.

Two Oregon National Guard F-15s, which took off from Portland, Ore., intercepted the plane and shadowed it until it landed at the Canadian base, NBC News reported.

The plane, a Boeing 777, had 147 people including 134 passengers on board, the airline said.

"The airline will decide about the continuation of the flight after discussion with the airport and related authorities," Korean Air said.

Royal Canadian Mounted Police Inspector Brian Massey told NBC News early Wednesday that cargo and luggage was being screened.

NBC News' Jim Miklaszewski and Courtney Kube, Reuters, The Associated Press and msnbc.com staff contributed to this report.

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