It is NOT easy to construct an atomic bomb, a fission weapon. It is even harder to build a hydrogen bomb, a thermonuclear fusion weapon.
The hard part to building a fission weapon is setting up the initial explosion which squeezes the fissionable material into critical mass. This initial set of explosions has to be timed so that the fissionable material is squeezed into critical mass without being blown apart. This is tricky to the point of impossibility absent a thorough knowledge of shaped charges and a supply of Klystron switches which make these charges explode at just the right time so that all the fissionable material is pushed inward producing the critical mass.
The hard part to building a fusion weapon is that you have to have a perfect fission weapon in order to produce the temperatures required to start a fusion reaction (thus THERMOnuclear reaction).
I'm no physicist, but I do understand that much. However if I'm an out of work Russian nuclear physicist with a family to feed, and you are a rogue state with plenty of money, a supply of fissionable material, and enough determination, we could likely reach some kind of understanding. This sceanario is likely to have been played out in the middle east more than once already. And perhaps in North Korea already also.
Unless all nations come to realize the ultimate soverignty of God, or whatever Higher Power you like, some nation is likely to feel its own soverignty to be threatened such as to be able to rationalize use of nukes on someone. I seriously doubt any nation could use a nuclear weapon on another country again absent immediate nuclear response from some other country. The circumstance surrounding our use of nuclear weapons on Japan, when we alone had the bomb, won't come again I don't think.
My two cents.
francoiss