TOKYO -- Daring defections by two malnourished North Korean soldiers across the Demilitarized Zone have highlighted a crack in the regime's armor.

More than 30,000 escapees from the North now live in South Korea. But cases involving front-line soldiers are "different from simple defections," as one defector put it.

Defections by soldiers pose a grave threat: Not only do they lower morale, they also suggest the regime is not as invincible as it seems.

One soldier crossed the DMZ on June 13, and another followed on June 23. Both are around the age of 20 and were found to be undernourished, according to South Korean media reports. The last time a North Korean soldier defected to the South was in September 2016.

The soldiers decided to flee because they had heard they would be given U.S. dollars in South Korea, they said.

Defecting through China is doable these days -- if you have the funds. "You can safely flee from the North if you pay 40,000 yuan to 50,000 yuan ($5,880 to $7,350) to a broker who bribes Chinese and North Korean border guards," a defector said.

There are even quite a few "repeat defectors," who shuttle between North Korea and China or South Korea, where they earn foreign currency.

Some upstream portions of the Tumen River, which separates China and North Korea, are less than 10 meters wide, allowing North Koreans to walk across the ice in the winter. Many sneak into China under the cover of darkness, find food, and return home later the same night, according to an ethnic Korean living on the Chinese side of the river.

It is a different story for North Korean soldiers staring down their South Korean counterparts across the DMZ.

The North Korean regime has buried a huge number of land mines in the DMZ in recent years. This is more about discouraging its soldiers from attempting to flee than warding off a South Korean intrusion.

In addition, the North reportedly runs a thorough brainwashing program to try to prevent front-line forces from longing for the South.

Behind the curtain

There was a time when North Korean soldiers were considered the ideal marriage partners, partly because they were entitled to ample rations. But the country's rationing system has become unworkable.

Senior officials of the ruling Workers' Party of Korea and the Korean People's Army, who live in Pyongyang, are still guaranteed sufficient rations in return for their absolute loyalty to the Kim Jong Un regime. In Potemkin village fashion, Pyongyang now features rows of high-rise condominiums, a growing number of fine restaurants and more than 3 million smartphones in use.

Elsewhere, citizens have been virtually cut off from the rations, forcing them to rely on illegal black markets, called jangmadang, to survive.

These markets started out as places to exchange farm produce and everyday goods for rice and other staples. They have grown to include a wider array of products brought in from China, according to defectors and other sources familiar with life in North Korea. More than 400 are scattered across the country.

The markets are always crowded because shoppers "can buy anything as long as they have money," a defector said.

Working around the regime's strict controls on citizens, shrewd merchants have bribed officials and established distribution systems covering almost the entire country. Merchants who control the supply and prices of key merchandise are now emerging as a new wealthy class.

The government was loath to allow this makeshift "market economy" to grow. But attempts to control the jangmadang were met with strong public resistance, so it now gives tacit approval.

Like most citizens, military personnel are scraping by -- besides high-ranking officers, that is. The armed forces collect rice from farmers and do some growing of their own, but a large portion of the output goes to the top brass.

Small rations are still available for the rank and file, but most young soldiers are said to be in a state of malnutrition.

In some ways, soldiers have even fewer options for easing their hunger. Unlike factory workers and farmers who can do side jobs, soldiers are already mobilized for farming and construction work. Under the circumstances, there has been a steep increase in cases of soldiers banding together for robberies and looting.

North Korean soldiers assigned to the DMZ also hear criticism of the regime blaring from South Korean loudspeakers. This may also tempt some to brave the land mines and defect.

All of this lays bare the contradictions at the heart of Kim's North Korea. While the leader is pushing an economic rehabilitation drive, it is clear that only the privileged class -- the critical class for preserving the regime -- will benefit.

Meanwhile, North Korea is pouring precious funds into its nuclear and missile programs, even as hunger drives its own soldiers to risk their lives to find better ones in the South.