Why was it so difficult for athen sans Sparta to defeat each other?

Athens and Sparta faced significant challenges in defeating each other due to their contrasting military strategies and societal structures. Athens relied on its powerful navy and superior trade networks, while Sparta had a formidable land army and a strong emphasis on discipline and training. Additionally, the Peloponnesian War saw both city-states forming shifting alliances, complicating their efforts to gain a decisive advantage. The resilience and resourcefulness of both sides contributed to a protracted and stalemated conflict.