As we noted last week when discussing President Donald Trump’s real strategy with North Korea, the big question following the Singapore summit will be verifying denuclearization. Recent history suggests this will be extraordinarily difficult.

First, there will be a constant struggle to get a brutal dictator to act openly and honestly in allowing inspectors to verify he has no ongoing nuclear program. The best case study of this problem is the decadelong effort of various UN-mandated inspection teams to gain access into Saddam Hussein’s covert facilities. From 1992 through 2003, Saddam played a shell game with inspectors trying to verify his regime had no nuclear, chemical or biological weapons. He refused access to various facilities, tried to sanitize facilities that might have had evidence of such weapons work, moved materials and equipment from one facility to another (or out of the country altogether), denied inspectors’ access to Iraqi scientists, and generally threw up every possible roadblock he could to make the inspectors’ work more difficult.

Saddam’s goal was simply to outlast the resolve of the UN and eventually get sanctions dropped and the inspections ended. He was assisted in his efforts by useful idiots, including within the UN, who accepted at face value the claims that a half-million Iraqi children had died as the result of sanctions, a claim later shown to be “a spectacular lie.” Saddam had come close to getting sanctions dropped by early 2001, and if the 9/11 attacks had not happened, he might well have outlasted the UN and had all sanctions and inspections stopped.

North Korea under the Kim-family regime is perfectly situated to play the same game. Kim Jong-un’s security forces are defiantly hostile to the United States and will undoubtedly attempt to deny access, intimidate inspectors, hide evidence, prevent access to scientists, and generally drag their feet. Even more so than most dictatorships, the Kim regime cannot tolerate losing face by accepting any and all requests for access to facilities or scientists. The humanitarian plight of the North Korean population is well known, and Kim will undoubtedly try to play on Western sensibilities to suggest his people would be able to eat if only the West would give North Korea a clean bill of health. Lastly, Kim and his advisers doubtless know that President Trump will not be in office forever, and a future president may be much easier to work with. Outlasting the resolve of the UN will be Kim’s primary goal.

A second problem will be identifying how many facilities North Korea has and assessing the role of each one in Kim’s nuclear program. The best case study of this problem is the ongoing effort to verify that Iran’s nuclear program is purely peaceful, an effort currently at 15 years and counting. If it was not for information provided by an Iranian dissident group in 2003, for example, the existence of an underground enrichment site at Natanz might never have been known. As recently as 2015, the same group provided evidence of additional sites near Tehran that were previously unknown. It is no coincidence that both facilities are deep underground. Iran has invested heavily in deep tunneling capability since the early 1990s in order to hide and harden both military and scientific facilities. Many of these facilities are known to Western intelligence services, but there are doubtless others whose existence is unknown.

North Korea has spent more than 60 years digging hundreds of miles of tunnels under its mountainous terrain, and it is unlikely more than a fraction of them are known to Western intelligence services. Satellite imagery cannot see what lies beneath the surface, and no nation on earth is more closed to human intel collection than is the well-named Hermit Kingdom. There is no North Korean dissident group outside the country that can provide information the way the Iranian dissident group could. In the absence of a comprehensive list of North Korean facilities, we will never know what portion of Kim’s program has even been identified, let alone inspected.

The Chinese will be crucial in addressing these two problems. No other nation has the kind of protective relationship with North Korea that China has, underscored by Kim’s recent trip to consult with Beijing. Yet China’s communist government is reflexively anti-U.S. and has taken every opportunity to prop up and even partner with nations around the world that are adversaries of the United States. China has long provided arms to Iran, for example, and has several massive energy deals with Tehran for developing and improving Iran’s oil and gas production.

In addition, China has all-important veto power at the UN, so any approach to North Korea will have to be tolerable to China (and to Russia, which is another headache entirely). The Chinese have historically been more eager to use North Korea as a bargaining chip, and changing their minds will not be easy. President Trump’s recent decision to instigate a trade war with China is aimed at exactly this problem. Whether that’s the right strategy is open for debate. But if the attempt to denuclearize North Korea is to have any chance of success, it will have to have Chinese buy-in. Whether that buy-in will be achieved cooperatively or coercively is the question.

Long story short, it’s one thing to have a summit; it’s another entirely to verify the agreed-upon terms.