“3/6 The territory of modern Donbas remained largely uninhabited for a long time and was known as the 'Wild Fields' (Dyke Pole). Only wild nomadic tribes appeared here occasionally (except for Greek settlements on the Azov Sea coast). I won't go into long and tedious stories about those nomadic tribes — the Polovtsians, Khazars, and others.
Until the 16th century (after the collapse of the Golden Horde), this area was a buffer zone between the Grand Duchy of Lithuania and the Crimean Khanate. On European maps of that time, it was depicted as empty steppe, or as 'Great Tartary,' or as part of the Crimean Khanate.
Nearby, Ukrainian Cossackdom was developing (part of Lithuania, and later the Polish-Lithuanian Commonwealth, but functioning like a 'state within a state' with its own elected leaders, laws, and courts). It was the Cossacks who started the real settlement of the 'Wild Fields' — the part we now call Donbas.
The first mention of Cossacks in these territories dates back to 1547 (one of the sources is the Nikon Chronicle). It is possible that Cossacks appeared there even earlier.
From the 17th century onward, this turned into regular, gradual settlement of the wild region by Ukrainians, continuing into the 18th century. This is confirmed in works by historians from various countries: Polish, Ukrainian, Russian, and French”
A history lesson of the Donbas