The map shows Greece during the Peloponnesian War. A map titled The Peloponnesian War. A key shows the location of the Peloponnesian War in purple, the Peloponnesian League in orange, and the Delian League in green. The Corinthian Isthmus is purple. Most of the southern peninsula of Greece around Sparta is orange. Crete, the Aegean Sea coastline including Athens, and all islands within the Aegean Sea are green.

Why was a strong navy important to the Delian League in the Peloponnesian War?

The island Delos was the capital of the Delian League.
A navy could cut off Sparta from mainland Greece.
Many islands made up the territories of the Delian League.
The Peloponnesian League could only attack Athens by sea.