Brest fortress originally was the largest 19th century fortress of the Russian Empire, one of the western Russian fortresses. It is located at the confluence of the Mukhavets and Bug rivers with total area 4 km². Its layout was developed by Russian general K.I.Opperman in 1830 and the initial phase of the construction lasted from 1836 until 1842. The fortifications were then progressively modernized and expanded throughout the 19th century, with forts added around the original fortress. The final works were carried out in 1914, the first year of World War I, culminating in a fortified area 30 km in circumference.
The fortress was captured by the German army in August 1915, after the Russian army abandoned it during its general withdrawal from Poland that summer. The fortress changed hands twice during the Polish-Soviet War and eventually stayed within Polish borders, a development that was formally recognised by the Treaty of Riga in 1921. In 1930, the fortress became notorious in Poland as a prison in the aftermath of the so-called «Brest elections» and the Brest trial. During the Invasion of Poland in 1939, the fortress was defended for four days by a small garrison of four infantry battalions and two tank companies under Gen. Konstanty Plisowski against the XIX Panzer Corps of Gen. Heinz Guderian. After four days of heavy fighting, the Polish forces withdrew southwards on 17 September.
On 17 September 1939, Russia invaded Poland and occupied the Eastern part of Poland including the Brest Fortress.
In the summer of 1941, it was defended by Soviet soldiers against the German Wehrmacht in the first days of Operation Barbarossa, earning it the title of Hero Fortress. The fortress had become a symbol of the Soviet resistance during the German-Soviet War, along with Stalingrad and Kursk, among others.