Since the Iranian sources provide no information about the establishment of the Medes Confederation, carrying out a study on this issue is only possible through the non-Iranian sources; although these sources differ, regarding their antiquity, authenticity, the arguments provided, and the fashion of presenting the data. The works of the Greek historians, specifically those of Herodotus and Tacitus have been the focus of attention for long, having been mainly adduced by recent researchers. Despite the contemporary scholars’ tendency to adduce to the works of Herodotus more than any other historian, in order to reconstruct the Medes Confederation, it should be mentioned that the works of Herodotus must be adduced circumspectly. Therefore, the key to the proper understanding of the history of the Medes is the appropriate recognition of the sources, accompanied by a critical view towards them.