ENDuring the war in the middle of the 17th century the privately owned city of Sluck was rebuilt to become one of the mightiest bastion fortresses in the Grand Duchy of Lithuania. The major role in these alterations belonged to the owner, duke Boguslaw Radziwill. The duke provided the fortifi ed city with highly qualifi ed military engineers and able administrators who supervised the construction of the fortifi cations. This paper makes use of the protocols of the sittings of the city council from 1654–1665 and of the correspondence of civil and military offi cial with duke Boguslaw to detail the organization of the construction of the fortifi cations, including the names of the specialists involved, as well as to describe the supply of man-force and materials for the construction works.