Silesian Przesieka

Silesian Przesieka, literally Silesian Cutting (Polish: Przesieka Śląska or Oseg, German: Schlesischer Grenzwald, Hag or Preseka, Latin: Indago) was a densely forested, uninhabited and unpassable strip of land in the middle of Silesia, spreading from Golden Mountains in the south, along the Nysa Kłodzka to the Odra, and then along the Stobrawa, reaching the towns of Namysłów and Byczyna in northern Silesia. Originally, the Silesian Cutting was a boundary, separating territories of two Western Slavic tribes, the Slezanie and the Opolanie. In the 12th century, along the Cutting a border of Lower Silesia and Upper Silesia was established.

For a long time, the Silesian Cutting was used as a natural military obstacle, protecting the area of Opole from raids of the Moravian and Czech tribes. However, it did not prevent the Hussites from invading Silesia in 1420 (see also Hussite Wars).

The Silesian Przesieka was a wide, uninhabited border forest, strengthened on the inside by cut-down trees whose branches were twisted together, with thick bushes and sometimes ramparts and trenches from the 8th–9th century blocking movements from the west. Gates, which could be closed in dangerous times, controlled all roads leading outwards. The Przesieka was maintained by local Polish peasants and used in their self-defence. If a settlement expanded in size the fortifications were moved outwards. Placenames like Osiek, Ossig, Hag, Hänchen Przesieka, Lower Silesian Voivodeship or Przesieka, Podlaskie Voivodeship commemorated these unique natural circumstances.

...
Wikipedia