Gacko

Gacko was a district of the Herzegovinian uplands crossed by the commercial route from Dubrovnik toward the Drina valley. Travellers passed through Cernica and the Gacko field before crossing the Čemerno pass. The surrounding country belonged to Sandalj Hranić and subsequently to Stjepan Vukčić Kosača, linking its roads and fortified centres to the lordship from which Herzegovina took its name.

Ključ, one of the district's important strongholds, is recorded in 1426 as a residence of the great duke Sandalj. Ottoman expansion brought Gacko under new authority during the 1460s; Ključ itself fell in 1468. From 1470 the district belonged to the Herzegovina sanjak. Gacko served as a judicial district, while Ključ housed military and administrative officers and became the seat of a captaincy in 1687. The name Gacko consequently embraced a wider territory with several centres, beyond the settlement that later bore it.