Sauron attempted to impose Black Speech as the official language of the lands he dominated (ultimately, to include all of Middle-earth) and all his servants, but he was only partially successful. The Nazgûl, the Olog-hai (the elite Battle Trolls of Mordor), and several of Sauron's major lieutenants and officers (e.g. the Mouth of Sauron) learned and used the Black Speech, but it never really caught on with the Orcs, or the various groups of Men from the east and south that Sauron conquered. The Orcs tended to corrupt and debase any language they were exposed to, so while Black Speech strongly influenced their vocabulary and perhaps grammar, it soon mutated into the myriad Orkish dialects, which are not mutually intelligible. By the end of the Third Age, while Orc vocabulary was peppered with certain terms from Black Speech, even they generally communicated using Westron, albeit heavily debased.