I remember reading a blog post by an, I assume, ex-muslima where she says that, during some of the islamic conquests the invading muslims invented a sort of drive-by-marriage which would last only a couple of hours/days. It's main purpose would be to make sex with female captives of war halal. My first question, is this true?
And if so, what was the need for it? I thought forced sex with female captives was legitimized during those times. Are there any comments on this practice by islamic scholars throughout history?
Sex with female slaves was always allowed. Concubinage was an accepted practice and children from those relationships were seen as equally legitimate as children from marriage.
Perhaps the person was referring to mutah marriage, which is a temporary marriage practiced by Shi'as. The marriage is self-expiring, i.e., when marrying, instead of "Till death do us part", it's "Till 3 months/weeks/days/hours are over". It has no relation to female slaves though.