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I’ve got some bad news for you about modern nuclear weapons.

All fusion weapons are fission weapons first (like a few nanoseconds first).

All fission weapons are not necessarily also fusion weapons. But probably most are nowadays.

Every nuclear weapon in the active US stockpile has a secondary fusion stage, the last pure fission weapons were removed from service and dismantled in 1992.

Most of the cost in a nuclear weapon is in the primary. It only makes sense to build pure fission weapons when you want very low-powered nukes for close range tactical use; the DoD has determined that don't see enough use for them to justify the upkeep of specific weapons.

The fission primary is used to trigger a secondary fusion reaction in modern weapons.

https://en.wikipedia.org/wiki/Thermonuclear_weapon

h-bombs do both

fission + fusion