Pan-Illyrian theories were proposed in the first half the twentieth century by philologists who thought that traces of Illyrian languages could be found in several parts of Europe, outside the Balkan area.
Pan-Illyrism had both archaeological and linguistic components. Archaeologists were looking for an ethnicity for the Lusatian culture and the linguists for the Old European water names. First, the French pressed for the Ligurs and Celts but then the German prehistorians and linguists, beginning with Gustaf Kossinna, and following Julius Pokorny, and Hans Krahe, linked the Illyrians with the Lusatian culture and Old European hydronyms. Kossinna divided the primitive Indo-Europeans into two groups, North and South Indo-Europeans; he conjectured that the ancestors of Celtic, Illyrian, Greek and Italic people, who belonged to the first group, inhabited north Germany in the Stone Age and Early Bronze Age and were driven out by Germanic people advancing from Schleswig-Holstein and Jutland about 1800–1700 BC "the first Germans in Germany". Kossinna also stated that at the time of Hallstatt culture which succeeded the Bronze Age of Central Europe, the Illyrian civilization of the valley of the middle Danube was superior to that prevailing among the Celts established in the southern portion of the Germany and elements of the Illyrian civilization found their way not only into the Celtic cradle of the south Germany but also to the territory of the east Germany occupied by Germanic tribes. The earliest use of iron in Central Europe was to be attributed to Illyrians and not to the Celts.
Julius Pokorny located the Urheimat between the Weser and the Vistula and east from that region where migration began around 2400 BC. Pokorny suggested that Illyrian elements were to be found in much of the continental Europe and also in the British Isles.