 The Korean Central News Agency claims the missile released three warheads, which were then guided to hit different targets. The report said the test was a step towards developing multiple independently targetable reentry vehicles, or MIRVs, which are harder to defend against than missiles with just one warhead. The U.S. deployed its first MIRVs in 1970. North Korean leader Kim Jong-un said he planned to develop his own in 2021.