Which of the following effects was a result of the Peloponnesian War?
Athens triumphed over Sparta and set up a democracy in Sparta.
The Greeks united to conquer Persia.
The Greeks were weakened and defeated by Philip II of Macedon.
Egypt conquered Greece.

The Peloponnesian War was an ancient Greek war fought by the Delian League led by Athens 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, Sicily; the attack failed disastrously, with the destruction of the entire force in 413 BC. This ushered in the final phase of the war, generally referred to either as the Decelean War, or the Ionian War. In this phase, Sparta, now receiving support from the Achaemenid Empire, supported rebellions in Athens's subject states in the Aegean Sea and Ionia, undermining Athens's empire, and, eventually, depriving the city of naval supremacy. The destruction of Athens's fleet in the Battle of Aegospotami effectively ended the war, and Athens surrendered in the following year. Corinth and Thebes demanded that Athens should be destroyed and all its citizens should be enslaved, but Sparta refused.

they wanted the u.s. to fight on the side of the central powers.