The area of the modern regional unit was part of the
Kingdom of Macedonia from the 8th century BC until the Third Macedonian War
(171 BC - 168 BC), when it became a part of the Roman Empire. At the division
of the Roman Empire in 395 AD, the area joined the eastern part, later known as
the Byzantine Empire. Between the 7th century and the 11th century, it changed
hands between the Byzantine Empire and the Bulgarian Empire repeatedly. In the
13th and 14th century Western Europeans and Serbs briefly ruled the area. The
Ottoman Empire conquered the area in 1371, and ruled it until the First Balkan
War of 1912. In the Second Balkan War of 1913, the Greek army captured the
area, which became part of Greece. It absorbed many of the Greeks from Northern
Macedonia (now the Rep. of Macedonia), especially from Gevgeli, Vogdantsa,
Polyane and Stromnitsa.
In the aftermath of the Balkan Wars, World War I and the
Greco-Turkish War (1919-1922) most of the Turkish and Bulgarian population of Kilkis
emigrated, and many Greeks from Bulgaria and Turkey settled in the area, as
prescribed by the Treaty of Lausanne. In fact, a very large segment of the
population of Kilkis regional unit are in origin Caucasus Greeks (that is,
Eastern Pontic Greeks) from the former Russian Imperial province of Kars Oblast
in the South Caucasus. They left their homeland in the South Caucasus for
Kilkis and other parts of Greek Macedonia, as well as southern Russia and
Georgia, between 1919 and 1921, that is, between the main Greece-Turkey
population exchange and Russia's cession of the Kars region back to Turkey as
part of the Treaty of Brest Litovsk.