:::::::: That Britannica uses the term, is indeed confirmation that the term exists; however, I'm not seeing justification for it to be a separate topic. It might be worth making something like a Wiktionary definition that "Mongol Nation" refers to the loose confederation of tribes that existed during the time of Genghis Khan, before the Empire started its major expansion.  Or, we could maybe add a couple sentences to that effect in the Mongol Empire article as a subsection, and then have "Mongol Nation" be a deep redirect to Mongol Empire#Mongol Nation. But I don't believe there's enough here for a separate article.