There is still a considerable about directly from fusion e.g. in the Tsar Bomba the fusion stage produced about 47Mt of the 50Mt total (it had two smaller H-bom

There is still a considerable about directly from fusion e.g. in the Tsar Bomba the fusion stage produced about 47Mt of the 50Mt total (it had two smaller H-bombs as primaries for the fusion stage). The full design was 100+ Mt so about 50% from the final fission stage seems a rule of thumb, which is also mentioned in this article about "neutron bombs": https://en.wikipedia.org/wiki/Neutron_bomb https://en.wikipedia.org/wiki/Neutron_bomb Neutron bombs don't have fissile tampers on the secondary exposing the neutrons from fusion directly rather than using them to fission the tamper.