In what / in which that / where that

Neither of your suggestions work for my ears, sorry. 'What' if replaced by 'that which' (not 'which that') would make the clause immeasurably awkward. 'What became known as his software phase' is a noun clause object of 'in', and is awkward enough as it is.

Hi MM

I should have said 'that which', which I saw before in your post. I just wanted to replace logically, but now I understand it's awkward.
What I don't understand is 'In what' in the original sentece is awkward, because I don't have a sence like yours. If you say this in another way, what is the first sentence(clause) like?

Thanks
Lij

Oh, I don't think it can be, LIJ-- it's just that that structure always seems overly formal to me: For what were to be the last years of his life; under what was to be the last dynasty of shoguns, etc.

I want to reach the level to see the two sentences you gave as expamples are over formal ones. You don't mean these sentences are not grammatically correct, do you?

LiJ

In what became known as his "software phase," Welch went to work rebuilding the confidence of the organization.
I think the 'In what' could be replaced by 'In which that'. Am I right? No. what is more like that which, not which that.

But I don't think replacing it by 'where that

I understand Thanks CJ and Mister.