Osowiec Fortress

Osowiec Fortress is a military complex in Osowiec-Twierdza in northeastern Poland, built along the Biebrza River. The site includes several defensive zones with concrete bunkers, earthen ramparts and brick forts linked by trenches and underground passages.

The Russian Empire began building the fortress in 1882 to defend its western frontiers against German advances. During World War I several battles took place here, including a poison gas attack in 1915 when Russian troops continued fighting despite heavy casualties.

The site takes its name from the nearby village and sits in marshland that has served as a natural barrier for centuries. Visitors can trace the layout of barracks and fortifications showing how soldiers lived in this remote border area.

Some areas lie within Biebrza National Park and can be visited with guided tours, while other sections remain in military use and are off-limits. Sturdy footwear is advisable as the ground can be marshy and uneven in places.

After the gas attack in 1915 Russian defenders charged forward despite severe injuries, surprising their opponents and forcing them to retreat. This incident later became known as the Attack of the Dead Men because the soldiers pressed on while already wounded.

Location: Osowiec-Twierdza

Inception: 1882

Founders: Russian Empire

Part of: WWI Eastern Front

GPS coordinates: 53.46861,22.64389

Latest update: December 12, 2025 23:01