The Brest Fortress

Fortress of War is a 2010 Russian-Belarusian war film recounting the June 1941 defense of Brest Fortress against invading Wehrmacht forces in the opening stages of Operation Barbarossa, Nazi Germany's invasion of the Soviet Union during World War II. Events are narrated from the perspective of 12-year-old Sasha Akimov, centering on three resistance zones holding out against the protracted German siege. The defending forces are led by regiment commander Major Pyotr Gavrilov, with Regimental Commissar Yefim Fomin, and the head of the 9th Frontier Outpost, Lieutenant Andrey Mitrofanovich Kizhevatov.

Synopsis from Wikipedia, CC BY-SA 4.0. Everything below written here.

Poster © the film's rights holders.