In Japan’s case, depending on what you mean they’ve already got IRBM (indeed, ICBM) capabilities. Their space industry has been building capable solid fuel boos

In Japan’s case, depending on what you mean they’ve already got IRBM (indeed, ICBM) capabilities. Their space industry has been building capable solid fuel boosters for a couple of decades. I assume they haven’t actually tested a precision guided reentry vehicle, but that’s all they’re missing on the missile side.