I'm currently writing a paper on the relative totality of warfare and came across a historian arguing that the most intense humanity has come in waging war was through the testing of the atomic bomb where they believed this could be the outcome. His footnote is a bit underwhelming though, a comment from a friend 'Aaron Novick' who was there and claimed this was the case. Hard to verify and wondered if anyone had any information on it. Would be interesting to hear anything about this. Thanks!
No. Their general opinion was that the atomic bombs couldn't "ignite" the atmosphere (the suggestion was that the bomb might be able to trigger a fusion reaction). The only dissenting opinion was Arthur Compton, who was not convinced of the complete impossibility of it, but he didn't think it likely (he estimated the probability at less than 1 in a million).
See https://www.reddit.com/r/AskHistorians/comments/c1jei5/is_it_true_fdr_authorized_a_test_during_ww2_that/ for more detail and references.
I've written a bit about the calculations that were done, and the people who weren't totally convinced of them, here. In short: they didn't really believe it was possible, but they weren't 100% sure. So when the bomb did go off, there were a few people who wondered, as the heat increased, if they had really "done it." But the bulk of the technical people had convinced themselves that it wasn't possible for several very good reasons. In the postwar it became very clear how difficult fusion reactions are to start and propagate.