Note that all U.S. nuclear weapons have PAL systems that cryptographically secure the nuke. These ensure that a.) the nuke can't be armed unless the President

Note that all U.S. nuclear weapons have PAL systems that cryptographically secure the nuke. These ensure that a.) the nuke can't be armed unless the President authorizes it b.) the nuke can't be armed unless at least two members of the chain of command responsible for the nuke authorize it and c.) the nuke can't be armed unless delivered in the manner expected. For example, a gravity bomb like the B-61 would have to be dropped from the height that nuclear weapons are expected to be dropped from. https://en.wikipedia.org/wiki/Permissive_Action_Link https://en.wikipedia.org/wiki/Permissive_Action_Link The worst that a hostile power could do with these nukes is to dismantle them, keep the plans to accelerate their own nuclear program, and store the raw nuclear materials. This is nothing to scoff at, but the threat model of "terrorist group steals nukes and blows up an American city" isn't actually realistic. Incidentally, this is why the Ukraine is not a major nuclear power. When the Soviet Union broke up a significant number of their nuclear weapons were physically located in the Ukraine, but the PAL codes were all generated in Moscow, and so the Ukrainians had a bunch of useless U-235 & explosives. They eventually destroyed the nukes because they were of no use.