This article examines the existing arguments of the Democratic Peace Theory on why democracies do not fight each other. It aims to summarize the most important aspects of the theory, and to provide adequate counterarguments. First, it explains the general implications of the theory, including its origins and explanations. Second, it explores the related critiques and controversies. Third, it identifies the theory’s practical application. Finally, it offers conclusions on how effective this theory could be during the present days.