Which pieces of classified information relating to nuclear weapons and warfare would you most like to know?

Questions of a classified nature are entertaining! Enough information exists as a public source that can paint generalities around technical specifics. For example, one can draw up their own likely SIOP with public information, but the fabric of reality relies on the limitations of delivery and weapon systems. So, the clearest picture of such requires knowledge that would also hint to weaknesses to exploit.

If you were given total access today, where would you start?