The UNSC stopped the Covenant in the end, but there was a heavy price paid. On Prophet's Price, fight a bloody close-quarters battle in the wreckage of a warship lost in action - some sections relatively intact, others open to space.
Note: due to an issue with Halo 5 file storage, the map may occasionally refer to itself as "Trafalgar". This is an old name for the map, which was changed before release. However, regardless of name inconsistencies, you are in fact on the right map.