The term 'Subject of Genghis Khan' can be summarized by two crossword solutions: TARTAR (6 letters) and TATAR (5 letters). TARTAR and TATAR are both terms used to refer to the Turkic-speaking people of the Mongol Empire, which was founded by Genghis Khan in the 13th century. The Tartars were a nomadic people who lived in the steppes of Central Asia and were known for their military prowess. The Tatars were a subgroup of the Tartars who settled in the Russian Empire and later became part of the Soviet Union.