TOKYO (AP) -- As tensions rise on the Korean Peninsula, one thing remains certain: All sides have good reason to avoid an all-out war. The last one, six decades ago, killed an estimated 4 million people.
A war would be suicidal for North Korea, which cannot expect to defeat the United States and successfully overrun South Korea. War would be horrific for the other side as well. South Korea could suffer staggering casualties. The U.S. would face a destabilized major ally, possible but unlikely nuclear or chemical weapons attacks on its forward-positioned bases, and dramatically increased tensions with North Korea's neighbor and Korean War ally, China.
Here's a look at the precarious balance of power that has kept the Korean Peninsula so close to conflict since the three-year war ended in 1953, and some of the strategic calculus behind why, despite the shrill rhetoric and seemingly reckless saber-rattling, leaders on both sides of the Demilitarized Zone have carefully avoided going back over the brink.
THE SEA OF FIRE
Even without nuclear weapons, North Korea has an ace in the hole. Most experts believe its claims to have enough conventional firepower from its artillery units to devastate the greater Seoul area, South Korea's bustling capital of 24 million. Such an attack would cause severe casualties -- often estimated in the hundreds of thousands -- in a very short period of time.
Many of these artillery batteries are already in place, dug in and very effectively camouflaged, which means that U.S. and South Korean forces cannot count on being able to take them out before they strike. Experts believe about 60 percent of North Korea's military assets are positioned relatively close to the Demilitarized Zone separating the countries.
North Korea's most threatening weapons are its 170 mm Koksan artillery guns, which are 14 meters long and can shoot conventional mortar ammunition 40 kilometers (25 miles). That's not quite enough to reach Seoul, which is 50 kilometers (30 miles) from the DMZ. But if they use rocket-assisted projectiles, the range increases to about 60 kilometers (37 miles). Chemical weapons fired from these guns could cause even greater mayhem.
North Korea experts Victor Cha and David Kang posted on the website of Foreign Policy magazine late last month that the North can fire 500,000 rounds of artillery on Seoul in the first hour of a conflict.
Even so, not everyone believes North Korea could make good on its "sea of fire" threats. Security expert Roger Cavazos, a former U.S. Army officer, wrote in a report for the Nautilus Institute last year that, among other things, North Korea's big guns have a high rate of firing duds, pose more of a threat to Seoul's less populated outer suburbs, and would be vulnerable to counterattack as soon as they start firing and reveal their location.
"North Korea occasionally threatens to "turn Seoul into a Sea of Fire," he wrote. "But can North Korea really do this? ... The short answer is they can't; but they can kill many tens of thousands of people, start a larger war and cause a tremendous amount of damage before ultimately losing their regime."
FIRST STRIKES, PRE-EMPTIVE STRIKES
This is what both sides say concerns them the most.
North Korea says it is developing nuclear weapons and long-range missiles as a deterrent to keep the United States or South Korea from attacking it first. The reasoning is that Washington will not launch a pre-emptive strike if North Korea has a good chance of getting off an immediate -- and devastating -- response of its own.
Along with its artillery aimed at Seoul and other targets in South Korea, North Korea is developing the capacity to deploy missiles that are mobile, thus easier to move or hide. North Korea already has Rodong missiles that have -- on paper at least -- a range of about 1,300 kilometers (800 miles), enough to reach several U.S. military bases in Japan. Along with 28,000 troops in South Korea, the U.S. has 50,000 troops based in Japan.
North Korea is not believed to be capable of making a nuclear weapon small enough to fit on a long-range missile capable of hitting the United States. But physicist David Albright, president of the Institute for Science and International Security, believes it may be capable of mounting nuclear warheads on Rodongs. In any case, Pyongyang is continuing to pursue advancements, apparently out of the belief that it needs nuclear-tipped missiles capable of reaching the U.S. to have a credible deterrent.