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