The same basic engineering and science needed to launch a satellite into space is also used in the multi-stage rockets known as inter-continental ballistic missiles. The front of the satellite rocket, according to three U.S. officials who work closely on North Korean proliferation, gave tangible proof that North Korea was building the missile’s cone at dimensions for a nuclear warhead, durable enough to be placed on a long-range missile that could re-enter the earth’s atmosphere from space.

“Having access to the missile front was a critical insight we had not had before,” one U.S. non-proliferation official told The Daily Beast. “I have seen a lot of drawings, but we had not seen the piece of that missile at that time.” This official continued: “we looked at the wreckage from the launch and we put it together with other kinds of intelligence and came to this judgment that they had figured out the warhead piece.”…

More recently though, other kinds of intelligence have also come to the attention of the U.S. intelligence community that suggest North Korea has mastered the miniaturization and warhead design work as well. Another U.S. official who works on North Korea work told the Beast that South Korea has recently shared more traditional kinds of intelligence with the United States about North Korea’s warhead design work, but did not get into the details of that intelligence.