It's Asia's nightmare scenario: War breaking out on the Korean peninsula.
With Korea lying at the heart of Northeast Asia, the world's third largest zone of economic activity after Western Europe and North America, experts say global capital markets would suffer devastating collateral damage, but the catastrophic loss of human life -- and potential nuclear fallout -- would be far, far worse.
Fortunately, no analysts believe "Korean War II" is imminent; the armistice ending the 1950-53 conflict that buried millions continues to hold, despite North Korea's nullification in March. And with regime maintenance Pyongyang's paramount policy, few think it would risk an attack.
But Kim Jong Un's experience and rationality is being questioned following his recent missile and nuclear tests, his annulment of the armistice and his bellicose vitriol -- extreme even by Pyongyang standards.
Despite annulling the armistice, a consistent Pyongyang demand has been a full peace treaty and it also wants direct talks with the United States, which Washington has resisted, preferring instead multilateral discussions.
Agreement with U.S.
Now, North Korea's actions are fueling concern; so much so that South Korea and the U.S. recently announced they had signed an agreement to firm up contingency plans should North Korea follow through on its threats.
It follows joint military exercises between the allies, which included flights by U.S. B-52 bombers over South Korea.
At the time, Pentagon spokesman George Little said the flights were to ensure the combined forces were "battle-trained and trained to employ air power to deter aggression."
Military strategists are clearly preparing for all eventualities. And it seems the South's citizens are also bracing for possible conflict.
The Asan Institute, a Seoul think tank, found that in 2012, ordinary South Koreans of all age groups believed war was more likely than not.
At present, a second 1950-style North Korean invasion seems unlikely, but possibilities that could ignite the peninsula tinderbox exist.
"I don't think any parties want all-out war, but scenarios to arrive at that outcome are some kind of miscalculation or inadvertent escalation," said Dan Pinkston, who heads the International Crisis Group's Seoul office. "The problem is that, considering recent developments, the escalation ladder has been getting shorter."
After fatal incidents in 2010, South Korea eased its rules of engagement, enabling speedier counter attacks to Northern attacks such as naval or artillery strikes.
And in February, South Korea's top general told Seoul's National Assembly of plans for pre-emptive strikes if intelligence indicated North Korean nuclear attack preparations.
Pre-emption is critical, given the close proximity of the two Koreas.
"Once we detect long range artillery and missiles being prepared, we would have no choice but to strike," said Kim Byung-ki, a professor at Seoul's Korea University; it takes only three minutes for a North Korean plane to reach Seoul, and under a minute for artillery shells to hit.
Analysts fear a limited Northern attack might provoke a Southern response, sparking a spiral of escalation and the dreaded "big war." With Seoul and Washington bound by treaty, America would have to commit. "Politically, the U.S. would have to be seen to support South Korea," said James Hardy, Asia Editor at defense publication IHS Jane's. "If it did not, its defense policy in Asia-Pacific would be in tatters."
North Korea's 1.1 million strong Korean People's Army, or KPA, is nearly double the size of the 640,000-person South Korean military and the 28,000 U.S. troops stationed in Korea.
Much of North Korea's military is believed to be decrepit: It lacks fuel, fields outdated equipment, and some troops are undernourished, but it wields two niche threats: special forces and artillery.
In a report in March last year, the commander of U.S. and U.N. forces in South Korea, General James Thurman, warned that North Korea has continued to improve the capabilities of the world's largest special operations force -- highly trained specialists in unconventional, high-risk missions.
Pyongyang fields 60,000 special forces, according to Gen. Thurman -- and more than 13,000 artillery pieces, most of it deeply dug in along the DMZ, and ranged on Seoul; the dense capital sprawls just 30 miles (48 kilometers) south of the border.
Moreover, with its main-force numbers and weight of firepower, the KPA might be able to concentrate offensive units with enough mass to punch across the fortified DMZ, through South Korean second echelon defenses, and barrel toward the Seoul region, an area with 24 million people.