An uncrewed, nuclear-capable submarine that creates massive radioactive waves to attack fleets of ships and render entire coastal cities uninhabitable. That’s how North Korea described its newly unveiled underwater attack drone.

#ONNanalysis 🧵
1.The DPRK reported on its 21-23 Mar nuclear counterattack drill where the “Haeil,” an “Unmanned Underwater Nuclear Attack Craft” designed to “destroy naval striker groups and major operational ports” via underwater explosion & “radioactive tsunami,” was revealed. pic.twitter.com/ylkU2JiPzE

— Open Nuclear Network (@OpenNuclear) March 24, 2023

It’s called the “Haeil,” which means tsunami in Korean. North Korea claimed it tested the new drone as the United States and South Korea wrapped up joint military drills.

North Korea said it started developing the Haeil 11 years ago, and it appears to share many characteristics with the Russian-made Poseidon torpedo. The Haeil is silent running, can be deployed from the coast or towed by a surface ship, and is designed to use stealth to infiltrate enemy ports and destroy them with a nuclear underwater explosion.

North Korea said it did not use nuclear weapons in the latest test of the Haeil. It’s unclear whether the country actually has the ability to put a miniaturized version of its nuclear warheads on the underwater attack drone. But Western intelligence officials did acknowledge North Korea is making strides in its nuclear ambitions.

The Haeil test was the culmination of three days of nuclear drills in North Korea. Those drills saw the launch of several cruise missiles and what appeared to be an inter-continental ballistic missile launched from an underground silo.

North Korean state media on Friday aired new footage of cruise missiles.

Pyongyang notably ramped up its missile testing in response to 11-day U.S.-ROK Freedom Shield joint drills.

(KCTV, Mar. 24)https://t.co/1C1scFn7wf pic.twitter.com/DNwIOEIilk

— NK NEWS (@nknewsorg) March 24, 2023

North Korean leader Kim Jong-Un was reportedly very satisfied with the drills. State media said Kim expressed his will to make “the U.S. imperialists and the [South] Korean puppet regime plunge into despair” over the powerful demonstrations.

Despair appeared to be in short supply in South Korea, though, as it wrapped up the largest joint military exercises the country’s held with the United States in years. For 11 days, U.S. and South Korean ground forces drilled side-by-side in simulated combat scenarios involving troops and heavy armor. The U.S. and South Korea also conducted five days of joint aerial drills. Another round of joint naval exercises is also on the docket.

The Associated Press and Reuters contributed to this report.