You have asked about whether nuclear devastation on this planet would affect the Sankirtana Movement. No, there is nothing that can stop the Sankirtana Movement because it is the will of God Himself, Lord Caitanya, that His Holy Name be heard in every town and village. Neither can the demons devastate this planet independent of the will of Krsna. Nothing happens without His sanction. If Krsna wants to kill someone no one can save him, and if Krsna wants to save someone no one can kill him. For our parts we should just be determined to carry out our mission against all opposition, demons, nuclear war, whatever. The whole universe is finally subject to certain annihilation by the will of Krsna, but devotional service is eternal and is the only certain way one can save himself from devastation. We can preach all over the world that the only way to be saved from collective and individual devastation is to take to the chanting of Hare Krsna. In short, this material world is a very precarious place therefore we should always chant Hare Krsna and seek Krsna’s protection.
From Srila Prabhupada’s letter to Makhanlal — Mayapur 22 June, 1973