During the Peloponnesian war, Sparta cut off Athens' supply of grain from the Hellespont in the Black Sea.
The Peloponnesian war was a long conflict between the Delian League, headed by Athens, and the Peloponnesian League, commanded by Sparta. It started in 431 BC and ended in 404 BC. Although it broke for issues between two minor poleis from both leagues, the conflict showed the tension for the balance of power in the Hellenic peninsula.
Sparta was famous for its disciplined army and had the advantage over Athens when fighting on land. Athens had a bigger and better navy and could control the seas.
Since the Peloponnesian League had besieged Athens, and destroyed its farming fields, the polis counted on the supply of grain coming from colonies in the Hellespont. This is why as a strategy, the Spartans cut off their supply of grain in 411 BC, to force Athens to surrender. However, the Athenian fleet managed to defeat the Spartan fleet near Cyzicus.
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