Terezin consisted of the Big Fortress and the Small Fortress. The Big Fortress was surrounded by ramparts and contained barracks. However, Terezin had not been used as a fortress since 1888; Terezin had become a garrison town that remained virtually the same, almost entirely separated from the rest of the countryside. The Small Fortress was used as a prison for dangerous criminals. Terezin changed dramatically when the Nazis renamed it Theresienstadt and sent the first Jewish transports there in November 1941. The Nazis sent approximately 1300 Jewish men on two transports to Theresienstadt. These workers made up the Aufbaukommando, later known in the camp as AK1 and AK2. These men were sent to transform the garrison town into a camp for Jews. The largest and most serious problem these workgroups faced was metamorphosing a town that in 1940 held approximately 7,000 residents into a concentration camp which needed to hold about 35,000 to 60,000 people.