The president went on to speak of the "32,000 soldiers, their finest equipment, barbed wire all over the place,” referring to the DMZ.
“We protect that whole thing. Nobody comes through,” he added.
The remarks caused groans of frustration from experts — both those who study immigration to the United States along its border with Mexico and the military standoff on the Korean Peninsula. Robert Kelly, an American who teaches international relations at Pusan National University in South Korea, shared a clip on Twitter.
“Cancel the Trump-Kim summit,” Kelly said. “Nobody should want a guy who talks like this to negotiate on behalf of democracy with [North] Korea.”
The border situation at the DMZ and the one along the frontier between Mexico and the United States are hard to compare directly. It is possible that Trump's comments, which appeared to be at least partially improvised, were designed to criticize what he saw as the unfair economic burden caused by the U.S. military presence in South Korea, a frequent target of his criticism.
But Trump isn't the first American to ponder the similarities of the DMZ and the Mexico-U. S. border. Questions about their similarities and differences have appeared several times on query-sharing websites such as Quora. Some experts, including Stephen R. Kelly, a retired American diplomat now at Duke University, have pondered the similarities, too — though Kelly concluded that Trump ought to "examine closely how this has worked out" for North Korea.
At the most basic level, the difference between the two situations is enormous. The “border” between North Korea and South Korea isn't really a border at all: It is the 1953 armistice line between the two Koreas. Since no peace treaty was ever signed after the Korean War, both sides are technically still at war and only observing a cease-fire.
The DMZ is designed as a buffer zone between the two opposing sides; its name is a misnomer, as the area is heavily militarized. In technical terms, neither side views it as a border; each views itself as the future government of the entire Korean Peninsula.
Mexico and the United States are not at war: They are friends and partners. Neither the current border nor the expanded wall suggested by Trump are designed to stop a Mexican invasion of the United States or vice versa. Instead, America's concerns about its border are related to smuggling and illegal immigration.
It may be true that few people or goods are smuggled across the DMZ, though it does sometimes happen. But South Korea isn't trying to keep the average North Korean citizen out. In fact, Seoul offers citizenship to refugees from the North. Almost all of these North Korean escapees, commonly dubbed “defectors,” travel through China and sometimes on to other countries before heading to South Korea.
If they could, many would probably try to go through the DMZ. What's holding them back isn't the South Korean army or its American allies — it's the North Koreans, who view defectors with contempt. Last November, when a North Korean soldier tried to escape across the DMZ, he was shot at least five times in a bid to prevent him from crossing over to the South Korean side. The soldier is now recuperating in the South.
In Pyongyang's eyes, the soldiers, barbed wire and other precautions such as mines along the DMZ are designed to stop an invading army from entering, or a traitor from escaping, by maiming or killing them. Neither Mexico nor the United States takes a similar view of smugglers or migrants crossing the border between their two nations.
The other big difference between the two situations is practical. The DMZ is about 160 miles long. The entire U.S.-Mexico border is about 1,969 miles. Even if Trump doesn't think the entirety of that border would require DMZ-style security — a point that would, in itself, undercut the comparison significantly — the length of the border would be several times longer than the DMZ.
Additionally, the DMZ is approximately 2.5 miles wide. Creating a border “zone” like this between Mexico and the United States would likely require taking private land, a move likely to be unpopular in the worst-hit places, such as Texas.
It is not clear where Trump got his figure for 32,000 soldiers at the DMZ and whether he is referring only to U.S. troops — he suggested earlier this month that the United States had that number “on the border between North and South Korea.” Recent figures show there are about 28,500 U.S. forces based in South Korea and that the majority are stationed at bases, rather than the DMZ itself.
Any understanding of the staffing costs for the DMZ would have to take into account that North Korea's army, one of the largest in the world, is thought to have around 750,000 troops acting as de facto “border security.” Mexico's entire military, including reserves, is around 418,000 people.
Given the numerous differences between the DMZ and the Mexico-U. S. border, it is hard to draw many lessons by comparing them. A more apt comparison when it comes to North Korea might be the country's northern border with China, its larger and economically more powerful neighbor. These two nations are allies, too. At 880 miles long, that border is more comparable to the U.S.-Mexico border.
But Trump probably wouldn't like the lessons from this border, where there is no wall and the smuggling of both goods and people is rife. And it would have been hard to complain about the burden on the U.S. military there, too.
More on WorldViews