North Korea's neighbors reported the country launched a missile on Thursday morning, and on Friday, Pyongyang said it wasn't just any missile: The regime claimed it tested a solid-fuel intercontinental ballistic missile (ICBM) for the first time, which the AP frames as "a possible breakthrough in its efforts to acquire a more powerful, harder-to-detect weapon targeting the continental United States."
South Korea's defense ministry on Friday confirmed it was a solid-fuel ICBM, reports the New York Times, but it indicated it did not believe the North had yet perfected the technology. Specifically, the AP acknowledges that "it remains unclear how far North Korea has come in mastering technologies to ensure the warhead would withstand atmospheric reentry and accurately strike targets." The so-called Hwasung-18 is the successor to the liquid-fueled Hwasung-17, which was tested last month and has the capability of reaching the US mainland.
The Guardian explains solid-fueled missiles have a leg-up over liquid ones in that the latter are fueled just prior to launch while the former are fueled when they are made, which cuts down on the time needed to prep them for launch—the difference can be minutes versus hours, reports Al-Jazeera. A researcher at the Asan Institute for Policy Studies in Seoul explains that it's not just a matter of efficiency: "The longer it takes after bringing out the missile from a silo or a tunnel, the higher the possibility of destruction before launch.” (More North Korea stories.)