The tower is in Via Quattro Novembre, in the area between the church of S. Caterina and the complex of the Mercati di Traiano. The name "Milizie" refers to the presence of roman militia emplacements or to a middle age garrison. The tower was settled at the beginning of the XIII century by Pope Gregorio IX from the family of the Conti. Following, it was bought and reinforced by Pope Bonifacio VIII. In 1348 an earthquake caused the falling down of the third floor and the sinking of the ground which caused the inclination of the tower still visible nowadays.The enlargement of the adjacent Church of S. Caterian in 1628, caused further damages to the tower as reported on an inscription walled up inside the ground floor. In 1914, some restoration and consolidation works were made by A. Munow and since 1927 is part of the complex of the Mercati Traianei.