The Peloponnesian War (431–404 BC) was an ancient Greek war fought by Athens and its empire against the Peloponnesian League led by Sparta. Historians have traditionally divided the war into three phases. In the first phase, the Archidamian War, Sparta launched repeated invasions of Attica, while Athens took advantage of its naval supremacy to raid the coast of the Peloponnese and attempt to suppress signs of unrest in its empire. This period of the war was concluded in 421 BC, with the signing of the Peace of Nicias. That treaty, however, was soon undermined by renewed fighting in the Peloponnese. In 415 BC, Athens dispatched a massive expeditionary force to attack Syracuse in Sicily; the attack failed disastrously, with the destruction of the entire force, in 413 BC. This ushered in the