North Korea’s first nuclear test was conducted in the Hamgyong Mountains 

 on 9 October 2006, the nuclear device was plutonium-fueled, and the explosion was under 1 kiloton. The explosion caused a artificial earthquake of 3.9 on the Richter scale. An anonymous official at the North Korean Embassy told a South Korean newspaper that the explosive output was smaller than expected. It was built under the command of Kim Jung-Il and took nearly 40 years to make as north Korea is a poor country  

The most recent missile test north Korea claims to have launched calling it Hwasong-8 the hypersonic missile “Hwasong-8 was topped with hypersonic gliding vehicle (HGV) warhead KCNA wrote”. hypersonic missiles are much faster almost 5 times faster than the speed of light and more agile which makes it harder to intercept with missile defense systems. North Korea joined a small group of countries trying to develop these weapons “including the United States, Russia, China and India”. With these new missiles they have made a new launching method with trains. And this was the third missile launched in the month of September 

The missiles now also have the fuel capacity to be launched into space and ready to be launched back towards earth, which also means it wouldn’t need to be fueled in a war and could instead be sent up earlier and used at any time during the war saving a lot of time.