In the UK it means "Monday Night Football", but in your question context, it probably means "Multi National Forces".
"“It happened all the time, not necessarily in MNF-West all the time, but throughout the whole country,” General Johnson testified, using a military abbreviation for allied forces in western Iraq. "
He's basically saying that, just because it happened in the MNF, it was nothing out of the ordinary as it was happening all over the country in equal measure.
Such massacre happened in the Multi National Forces? Should "happened in" been "was committed by"?