Minor nitpick: your yield numbers are a bit high. The highest-yield nuke in the US arsenal is the B83: https://en.wikipedia.org/wiki/B83_nuclear_bomb https://e

Minor nitpick: your yield numbers are a bit high. The highest-yield nuke in the US arsenal is the B83: https://en.wikipedia.org/wiki/B83_nuclear_bomb https://en.wikipedia.org/wiki/B83_nuclear_bomb It can be dialed up to max 1.2 megaton. Yields have come down since the 60s as delivery became more precise (you need less bang to kill a target if you can get closer) and MIRVs made it more efficient to put multiple devices on the same missile (they can spread out the bang over a larger target area, and as you say, they provide redundancy against countermeasures).