The author relies on the thesis that the main factor in the development of Western European diplomacy in the early Modern period was the emergence and formation of the resident diplomacy. The article proposes a periodization of the development of diplomacy, based on an understanding of the development of Western European diplomacy in the 15th –16th centuries in the context of the transformation of the medieval socio-political model.Under the conditions of permanent internal and external political pressure, the medieval hierarchical model of the socio-political structure did not fulfill the function of legitimizing the new regimes on the Apennine peninsula. The peace of Lodi in 1454 consolidated the heterarchical or polycentric model of the socio-political structure, which assumed mutual recognition of the subjects of interstate relations as a source of legitimacy.In the second half of the 15th century this model, based on a network of stable diplomatic relations, was adopted by most of the major Italian states. Italian wars of 1494–1559 influenced the spread of the new style of diplomacy with its resident envoys to the leading states of Western Europe.Despite the crisis of the second half of the 16th century the model of a resident diplomatic representation has become the basic one in the European diplomacy of Modern age.