Soviet POW camps in Estonia
After the Soviet occupation was restored in 1944, a number of forced-labour and prisoner-of-war camps were set up in Estonia. In 1944–1953 dozens of camps and camp points operated in Estonia. Prisoners of war (mostly Germans) were held in separate GUPVI-system camps; political prisoners were largely sent to Gulag camps outside Estonia.
GUPVI and the Gulag
The POW camps were run by the Department for Prisoners of War and Internees of the Estonian SSR's People's Commissariat of Internal Affairs (NKVD), which put the prisoners to forced labour. In 1944–1946 about 20,000 people were arrested in Estonia, most of them sent to Gulag camps outside the country.
Camps in Estonia
The largest and best known were the Kohtla-Järve POW camp (No. 289), the Maardu POW camp and filtration camp No. 0316. Prisoners were used, among other things, on the Tallinn–Narva highway and in the oil-shale and chemical industries. Patarei prison served both occupations.
See also the overview of the camps. Sources: Soviet POW camps in Estonia (Wikipedia) and A little-known branch of the Gulag (Communist Crimes).