The concentration camp operated from May 1918 to 15 September 1918 when the majority of the captured Reds were released on parole.

Inmates died of malnutrition and various disease, including the Spanish influenza that caught Finland in July.

[3] According to the War Victims of Finland 1914–1922 internet database, a total number of 2,997 prisoners died in Tammisaari between May and December 1918.

[5] After the mass amnesties of the Civil War prisoners Tammisaari penitentiary was turned into a labor camp for political prisoners, meaning the activists of the banned Communist Party of Finland and Socialist Workers' Party of Finland.

As the communists spent a lot of time in reading and studying smuggled Marxist literature, the camp was nicknamed the "University of Tammisaari".