In a war many thermonuclear weapons would be targeted at hardened military structures and so detonate close to the ground to maximize local pressure. In a scen

In a war many thermonuclear weapons would be targeted at hardened military structures and so detonate close to the ground to maximize local pressure. In a scenario like that you'll get a large amount of fallout just from neutron activation of what was once the ground and the bomb casing won't expecially matter.