The complex of defence in the village of Sutkivtsi in Podolia is one of the unique fortification monuments of Ukraine. It consists of two objects ‒ a defence church that belongs to the quadrifolium type, and a protobastion castle (built on the site of a 13th–14th century fortified settlement), located on two dominant neighboring hills, and with a settlement located in a narrow valley in between. The long theoretical dispute about the founding date of the quadrifolium, with no analogues in Ukraine, was mostly resolved during the restoration works in 2006–2010, that were carried out by the author of this article. It was found that at the first stage of construction (XIII century), the object was not associated with a sacred function, and was playing the role of a defensive tower. Its transformation into a temple in the 15th century was connected with the appearance on the site of the fortified settlement of a regular five-tower castle, which took over the main defensive function. The existence of three defensive structures in Sutkivtsi (a fortified settlement, a quadrifolium, and a castle) witnesses the strategic importance of the settlement and arouses interest in the stages of its formation. Permanent defensive activity, in the time of difficult historical and political conditions of Podolia’s opposition to nomad raids, allows us to consider the evolution of the complex as a chain of stadial transformations, reflecting innovations in the art of fortification and adaptations to changes in arhitectura militaris, in particular, to the tactics of fortress siege and defense. One of the characteristic features of the complex is its topographic two-component nature, which the fortification architects had taken into account at each stage of modernization. The important question for understanding the goals and objectives of each transformation is to establish whether the fortification works of both components of the complex were carried out simultaneously, or in sequence that was characterized by the «pendulum» principle.