From the 16th century, the Danubian basin became the natural battleground of repeated wars between the Ottomans and the Habsburgs. After relieving the third Siege of Vienna (1683) and further victories confirmed by the Treaty of Passarowitz (1718), the Habsburgs could finally expel the Ottomans from the basin, and embarked on a policy of repopulating the devastated territory from other parts of their empire. The settlers came from as far afield as Alsace and the Ukraine, but were collectively referred to as Swabians by both the imperial governors and the region’s native population, from the patois they developed. Although the region remained under threat (the Ottomans invaded again in 1737), military governors like Count Florimond de Mercy proved enlightened landowners, restoring the agrarian economy. However, the complex admixture of ethnicities and religions the migration helped to establish would contribute to Balkan instability in the 19th and 20th centuries.