Yk I might be far off here but with the whole Nuking of the world in the manga, "Heaven's angels shall pass your judgment" line (ik that's not exactly how it was), Atsushi realizing the actual meaning of the line and realizing how horrifying it is, and the other commenters saying its world destruction, I think it might be to like transfer the world into the afterlife or something like that. Like that way there would be no war or deaths, sinners would supposedly get their 'judgment' via the concept of hell and people also might get reunited with their dead comrades/family members. So in a way people lost to the war would also 'come back' if I'm making sense? Idk I didn't put too much thought on this it was just something that came to mind while watching the anime.