I was reading Tito's account of a battle from World War I and he mentions a description of 'Circassians' at one point. I don't know much about the various ethnic groups in Russia, but Cossacks and Circassians especially confuse me. I always understood Circassian to just be another term for Caucasus, but now I know that clearly isn't the case? Are the Circassians a clearly defined ethnic group? Why did they have so many army units just made up of themselves, then?