How did the Athenian empire fall?

Answer 1

Athens became involved in what has become known as the Peloponnesian War in 431 BCE against Sparta and its allies. It expected, by withdrawing its populace inside its walls, to be able to withstand a seige indefinitely, as its 'long walls' connected the city to its fortified port, Piraeos, and so it could be resupplied. From the port also could its vastly superior navy continue to operate - to collect tribute to pay for food and the navy, and also to raid the Spartan league lands. It looked a good deal. However Athens over-reached itself in trying to conquer Syracuse to give it dominance over the resources of Sicily, which ended up with total loss of the army and navy sent there. Then the Persians intervened, giving Sparta the money to build up a league navy able to match Athens'. The Spartan league eventually destroyed the Athenian navy, invested the city and after Athens surrendered in 404 BCE because it could not import food, stripped it of what remained of its empire. In the process of this 27 year war, the Hellenic world suffered great damage. And it did not end strife and result in a settlement either, as different alignments of city-states continued to fight each other for several decades. This allowed the King of Persia to intervene again in Greek affairs - this time not as an invader but as an imposer of peace.