[lbearl]

I'm guessing you just mis-typed, but I think you meant nuclear instead of chemical.

[bcmit]

No, I think he's talking about the initial, chemical explosion that sets off the fission + fusion part, at least in the old bombs.

[curtis]

That's right. Note that there are other Z-pinch fusion designs which use the Z-pinch to directly trigger fusion reaction without going through a fission intermediary.