North Korea also has a large but nearly completely obsolete air force. The only aircraft Pyongyang possesses that might marginally threaten American airpower are its small fleet of Mikoyan MiG-29 Fulcrums. “They supposedly have up to 40 MiG-29s, but I’m not sure how many of them are still airworthy but some surely are,” Kashin said. “Pilot training is limited and never exceeds 20 flight hours per year.”

If the Trump Administration chooses to intervene in North Korea, the White House may discover that Pyongyang is a more formidable adversary than many might expect.

Aside from the reclusive regime’s nuclear weapons, Kim Jong-un’s hermit kingdom boasts air defenses that are more advanced than many might realize. Moreover, Pyongyang has also taken steps to increase its resilience against any aerial onslaught that that United States might launch in the event of war. The so-called Democratic People’s Republic of Korea has not forgotten the lessons of the Korean War–which technically has not yet ended.

(This first appeared last year.)

“Between 1950 and 1953, the U.S. Air Force and Navy flattened North Korea, so the NORKS have had 65 years to think about how to make sure that does not happen again and dig lots of bomb proof shelters and tunnels,” retired Rear Adm. Mike McDevitt, a senior fellow at the Center for Naval Analyses, told The National Interest.

But aside from hardening its facilities, Pyongyang fields more advanced air defenses than one might assume. While the overwhelming majority of North Korean air defenses are older Soviet systems, Pyongyang does field some surprisingly capable indigenous weapons.

“They have a mix of old Soviet SAMs [surface-to-air missiles], including the S-75, S-125, S-200 and Kvadrat, which are likely in more or less good condition,” Vasily Kashin, a senior fellow at the Center for Comprehensive European and International Studies at Moscow’s Higher School of Economics told The National Interest. “They used to produce the S-75 themselves—and those could have received some significant upgrades. In addition to them, since early the 2010s they are fielding an indigenous modern SAM system which is called KN-06 by South Korea and the U.S.”

It is not clear how many KN-06 SAM batteries Pyongyang has built, but the North Korean weapon is a surprisingly capable system that is similar to early model versions of the Russian-built S-300. “No one knows exactly how many such systems exist,” Kashin said. “The KN-06 has phased array radar and tracks via missile guidance system and maybe equivalent to the early S-300P versions but with greater range.”

Kashin—who is a specialist on Asian matters—said that South Koreans sources have written that the KN-06 has been successfully tested. The weapon is thought to have a range of up to 150 km. One of the reasons that the KN-06 is often ignored—even though information is available about the North Korean weapon—is that Western analysts often underestimate Pyongyang’s industrial capabilities.

“Generally, there is a great underestimation of North Korean industrial capabilities in the world,” Kashin said. “From what I know, they do produce some computerized machine tools and industrial robotics, fiber-optics, some semiconductors as well as a variety of trucks and cars, railroad rolling stock, consumer electronics etc. So they can do something comparable to Soviet designs of the 1970s to early 80s—especially when they cooperate with the Iranians.”

North Korean low altitude air defenses are also fairly robust—even if the systems that Pyongyang fields are dated. “At low altitudes, they have huge numbers of license produced and indigenous MANPADs [man-portable air defenses] and 23-57mm anti-aircraft artillery—many thousands of pieces,” Kashin said.

North Korea also has a large but nearly completely obsolete air force. The only aircraft Pyongyang possesses that might marginally threaten American airpower are its small fleet of Mikoyan MiG-29 Fulcrums. “They supposedly have up to 40 MiG-29s, but I’m not sure how many of them are still airworthy but some surely are,” Kashin said. “Pilot training is limited and never exceeds 20 flight hours per year.”

However, while North Korean technology is relatively primitive—the nation’s air defenses are coordinated. “They do have an old Soviet computerized anti-aircraft command and control system. Most of the radars are old, but they did receive some newer Iranian phased array radars,” Kashin said. “This is what I know, the anti-aircraft units are extensively using underground shelters for cover—not easy to destroy.”

Thus, while generally primitive, North Korean defenses might be a tougher nut to crack than many might expect. Moreover, while their technology is old, North Korea’s philosophy of self-reliance means it can produce most of its own military hardware. “They produce a lot of stuff, although in many cases the technology would lag some 20 to 40 years behind,” Kashin said. “But they do produce it independently.”

Dave Majumdar is the former defense editor for The National Interest.