On December 21, the North Korea state television aired a footage of its unannounced submarine missile test. The live footage included Kim Jong-Un with a winter coat and fedora hat looking at a missile launching from underwater which immediately switches to a rocket flying through the air and disappearing to the clouds. This was the third missile test North Korea conducted after its first missile test in May and the world has been greatly aware of how hard North Korea has been putting to develop the SLBM (submarine-launched ballistic missile), which is a ballistic missile that would be launched from a submarines.
Immediately after this video was aired by the North Korean state television, it attracted many viewers from all around the world including many experts. Many people and experts credited this video as fake, especially the South Korean military that said North Korea modified the video and edited it with a missile footage from 2014. Further evidence for North Korea splicing the video into two parts was given by the James-Martin Center, who covered the failure of the launching of the missile with heavy video editing to cover this fact. Experts such as Melissa Hanham, a senior research associate of the Middlebury Institute supported this claim along with additional facts that the North Korean media used different camera angles and rudimentary editing techniques to cover up the failure, but he states that this covering up was really evident.
For these reasons, experts think that the bomb blew up right after its launch. Along with the failure of the third missile launch, the second missile launch test by North Korea is also believed to be a failure, in support to the claims by various South-Korean intelligence reports.
It still remains unclear whether North Korea was truly successful in launching its third missile test since it did not make any official announcement after the launching happened, but it made an opinion that its most recent nuclear test was more advanced and powerful than the hydrogen bomb of the U.S. Although this statement brings a lot of skepticism and not many people believe this to be true, no one truly knows and will never know what it happening in North Korea right now.