'in doing sth'

[peteryoung]

In unifying all the land that had once been in the Chou domain, he renamed the national dynasty Ch'in, which became China.

What does 'in' mean here? 'when'? 'after'? or ..
Any reply'd be appreciated.

[Mister Micawber]

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Actually, it seems a trifle odd, Peter, because of the actual context, but I presume 'in' means 'in the process of', 'in the course of'.

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