Slavs
Slavs are an Indo-European ethno-linguistic group who speak the various Slavic languages of the larger Balto-Slavic linguistic group. They are native to Eurasia, stretching from Central, Eastern, and Southeastern Europe all the way north and eastwards to Northeast Europe, Northern Asia (Siberia), the Caucasus, and Central Asia (especially Kazakhstan and Turkmenistan) as well as historically in Western Europe (particularly in East Germany) and Western Asia (including Anatolia). From the early 6th century they spread to inhabit the majority of Central, Eastern and Southeastern Europe. Today, there is a large Slavic diaspora throughout North America, particularly in the United States and Canada as a result of immigration.
Czechoslovak–Hungarian population exchange
"We have decided now that our liberated State shall be a national state, rid of all hostile elements, living in brotherly harmony with the family of Slav States and in friendship with all peace-loving nations of the world. (§ 9) [...] The Czechoslovak Republic is a unitary State of two Slav nations possessing equal rights, the Czechs and the Slovaks." (Article II/1 )"