Final answer:
Greece is the country that has the Gulf of Corinth, separating the Peloponnese from the mainland. The Peloponnesian War saw Athens and Sparta leading opposing alliances, with Athens being a strong naval power and Sparta being land-based.
Step-by-step explanation:
The country that has the Gulf of Corinth, a deep inlet of the Ionian Sea separating the Peloponnese from the rest of Greece, is Greece. The Peloponnesian War, a significant historical event involving many Greek city-states, featured two primary leaders of their respective alliances. The two Greek city-states that led these alliances were Athens and Sparta. Sparta, centered on the Peloponnese, was largely a land-based force, while Athens, located to the north of the Peloponnese across the Gulf of Corinth, controlled the coastlines and islands of the Aegean Sea, demonstrating strong naval power.
Throughout this war, Athens and Sparta clashed for dominance over the Greek world, which at this time included extensive maritime routes and knowledge of regions as distant as the Black Sea and Persia. Greek culture valued exploration and trade, impacting their interactions with surrounding civilizations. Despite the Greek city-states being relatively small and disunited, their shared victories in the Persian Wars led to increased confidence and the establishment of a civilization marked by significant cultural and intellectual achievements during the Classical Age.