Several years ago, a small group of executives who invested in Kaesong chatted casually of even more grandiose plans: eventually, 10 Kaesong-like facilities in the North, employing 5 million total — one-fifth of the country.

“That was our vision,” said Song Ki-suk, a now-departed executive at an automobile components company that went into Kaesong…

Today, Kaesong is a grid of gray factories. Ninety percent of the master plan is undeveloped, and investment was frozen when North Korea launched a pair of attacks on the South in 2010. Business executives there say they’re at the whims of North Korea’s 30-year-old ruler, Kim Jong Un, who last Wednesday barred South Koreans from entering the plant, perhaps as a political show of force.

The barricade, now four days old, has potentially fatal implications for the companies at the plant, who are late distributing products to customers.