Can we have a little chat about Tatars and Tartars? I see these names used incorrectly all the time in all sorts of places, many of which should know better. Of course most people don't care, but I do.
The Tatars are a Turkic-speaking people living mostly in Russia. The name is pronounced Ta-TAR, at least by the Tatars we know. There is quite a bit of diversity among the Tatars though and they certainly don't just live in Russia. They also have a very interesting history depending on where they live.
Tartar is the name Europeans applied to the Mongols when they were harassing Europe. Tartarus is the name of a Greek god of the underworld and the name was confused with the Tatars who lived west of the Mongols at the time. The Europeans apparently thought it was a more fitting appellation for the Mongols.
This is all well and good, but Tartar has hung around for far too long. The names Tartar and Tartary started to be applied to all sorts of peoples and places from Siberia to Tibet. That means you often can't even tell who is being referenced when the term is used. Are they Tatars? Kyrgyz? Sakha? Turkic-speaking people? Mongolians? People who aren't like me? Who knows? It's not a modern name and it really has no modern use. It also has a derogatory connotation.
When you're reading history books or other types of books about Eurasia and they call the Tatars Tartars or use the words interchangeably for various groups of people, it's not impressive. As a general rule, if you're talking about a modern person or place, don't ever use Tartar or Tartary. And if you're dealing with history, there are many more specific words that can be used to identify the various people living in Central Asia.