Until 1918, the Ossowiec Fortress, located on the banks of the Bobr River, was part of the Russian Empire and is now situated in Poland. Its construction began in the 1880s and was completed in the 1890s to strengthen the northern borders and protect the important transport hub of the city of Bialystok. The design was carried out by fortification engineer Eduard Totleben. A total of four forts were built, surrounded by protective moats.

By the beginning of World War I, the fortress housed one infantry regiment, two artillery battalions, a sapper unit, and a support unit. At the onset of hostilities, the garrison successfully repelled three enemy assaults, one of which was accompanied by a heavy gas attack. In 1915, Russian troops abandoned the fortress.

An intriguing legend is associated with this fortress, though it is not documented. In the 1920s, Polish and Soviet publications reported on a Russian soldier found by Polish authorities in the Ossowiec Fortress. It turned out that during the retreat, the sappers had buried underground ammunition and food depots with explosions. When Polish officers descended into the cellars, a voice called out from the darkness: "Halt! Who goes there?" The stranger turned out to be Russian. He strictly adhered to military regulations and stated that only the officer of the day or the "Emperor" could relieve him of duty. The soldier surrendered only after being informed that the country he served no longer existed. For 9 years, he survived on canned meat and condensed milk, keeping track of time and adapting to life in the dark. After emerging into the light, he lost his sight and was placed in a hospital, then handed over to Soviet authorities.