Prince Janusz Radziwiłł lost about 43,700 hectares to Soviet and communist seizure, and his wife died in NKVD custody

Janusz Radziwiłł was born in Berlin in 1880 into one of the richest families of the old Polish-Lithuanian Commonwealth. He was Polish foreign minister in 1920-1921 and later a senator. After his father died in 1926 he held about 43,700 hectares: forests and sawmills at Cumań, estates at Szpanów, Ołyka and Nieborów, and a palace on Bielańska Street in Warsaw^†. On 20 September 1939, after the Soviet invasion, the NKVD arrested him with his son Edmund^†. He was held in the Lubyanka prison in Moscow and questioned by Lavrentiy Beria^†. He was freed after about three months following Italian intervention. The Red Army also expelled the family's Nieśwież line from Nieśwież Castle, where Radziwiłł coffins lie in the Corpus Christi Church. In January 1945 the NKVD arrested Janusz again with his wife Anna. On 4 March they were taken to Krasnogorsk near Moscow. Anna died there in 1947. Janusz returned to Warsaw in 1947 with no property and lived in a small flat. Nieborów became a branch of the National Museum in Warsaw. Ołyka, now in Ukraine, became a psychiatric hospital. He died in Warsaw on 4 October 1967. In 1972 his remains were moved to the Radziwiłł crypt at Wilanów^†. In 2026 Nieborów is a state museum, Ołyka Castle has belonged to the Volyn regional museum since 2021, and Nieśwież Castle is a Belarusian state museum and a UNESCO site since 2005.