It is also true that the Imperial Japanese Navy was able to surprise us at Pearl Harbor only once. It wasn't like a regular thing, so that is some comfort, right?
If you can produce one, you can produce two, If you can produce two you can produce two dozen.
Of course Mass production does not come until you get all the kinks worked out, but the N. Koreans seem to be doing allright in that capacity. You have to give them credit they are gaining expertise every day.