Brestskaya krepost deals with the surprising German attack on the Soviet Union in June 1941. The Russian soldiers based at Brest fortress seem to lead a peaceful and safe life with their families. The fifteen-year old orphan Sasha, who is a trumpeter in the music corps, enjoys the time with his girlfriend Anya. The idyll finds a sudden end as German forces start their brutal assault on the fortress on 22 June. In the face of the attack, the citizen in Brest start to panic. A lot of them die or get wounded. Also Sasha suddenly found himself in the middle of the bloody events of war. Despite military inferiority and heavy losses, the Russian soldiers under the guidance of the officers Gavrilov, Kischevatov and Fomin first succeed in striking back the enemy troops. As a result, the Germans react with heavy bombardment and the siege of the fortress. In view of the catastrophic supply situation, finally the three officers decide to try to break through the hostile lines.