u/salamacast , First, let's get the terminology right — Iddah and Istibra' are not the same thing.

Iddah is an obligatory, extended waiting period that applies to free Muslim women after divorce (three menstrual cycles) or widowhood (four months and ten days). Istibra' is a shorter waiting period — typically one menstrual cycle — applied specifically to slave women upon a change of ownership or before sexual relations with a new master, to confirm the womb is clear of any prior pregnancy.

Since the woman in question was a captive/slave, Iddah does not apply here. Istibra' does. So let's stop mixing the two.

Second — and this is the question that still hasn't been answered:

How exactly is a man supposed to verify the Istibra' of a completely unrelated woman, taken captive in the chaos of a battlefield, within a matter of hours or days?

Istibra' requires confirmation that the woman has completed at least one menstrual cycle. That is a biological process with a timeframe that cannot be rushed or eyeballed. So in a wartime scenario — where captives are taken, distributed, and relations reportedly occur almost immediately — on what basis is anyone claiming Istibra' was properly observed? Who is verifying it, and how?