> Tolkein of course denied this .... and the timing wasn't right

Just to expand on this, substantial portions of LOTR were written well before the atomic bomb became public knowledge, e.g. Tolkien had written first drafts of Book 4 (Frodo's journey to Mordor with Sam and Gollum) by 1944. In other words, it was already a fundamental plot point that the ring should not be used even as an ultimate weapon.

The depiction of war in LOTR is perhaps more closely associated with Tolkien's personal experiences in the war of 1914-18. The dead marshes in particular have similarities to the trenches of WW1