Thucydides informs us that the cause of the Lacednmonians was the more popular, as they professed to be deliverers of Greece, while the Athenians were fighting in defence of an empire which had become odious through their tyranny, and to which the states which yet retained their independence feared to be brought into subjection.
In the summer of the year 43L R.e., the Peloponnesians invaded Attica under the command of Archidamus, king of .Sparta. Their progress was 'slow, as Archidamns, their commander, appears to have been still anxious to try what could be done by intimidating the Athenians before proceeding to extremities. Yet their presence was found to be a greater calamity than the people anticipated ; and when Archidamus made his appearance at Achanam, they began loudly to demand to be led out to battle. Pericles firmly adhered to his plan of defence, and the Peloponnesians returned home. Before their depar ture the Athenians had sent out a fleet of one hundred sail, which was joined by fifty Corcyrean ships to waste the coasts of Peloponnesus; and towards the autumn Pericles led the whole disposable force of the city into Megaris, which he Laid waste. In the same summer the Athenians expelled the inhabitants of iEgina from their island, which they colonised with Athenian settlers. In the winter there was a public funeral at Athens for those who had fallen in the war, and Pericles pronounced over them an oration, the substance of which is preserved by Thucydidcs (ii. 35-46).
In the following summer (B.c. 430) the Peloponnesians again invaded Attica under Arehidamus, who now entirely laid aside the forbearance which he had shown the year before, and left scarcely a corner of the land unravaged. This invasion lasted forty days. In the meantime grievous pestilence broke out in Athens, and raged with the more virulence on account of the ctowded state of the city. Of this terrible visitation Thucydides, who himself was a sufferer, has left a minute and apparently faithful description (ii. 46, rte.). The murmurs of the people against Pericles were renewed, and he was compelled to call an assembly to defend his policy. He succeeded so far as to prevent any overtures for peace being made to the Lacedremonians, but lie himself was fined, though immediately afterwards he was re-elected general. Wh4e the Peloponnesians were in Attica, Pericles led a fleet to ravage the coasts of Peloponnesus. lu the winter of this year Potichea surrendered to the Athenians on favourable terms. (Thucyd.,
ii. 70.) The next year (B.c. 429), instead of invading Attica, the Pelopon nesians laid siege to Platrea. Tho brave resistance of the inhabitants forced their enemies to convert the siege into a blockade. In the same summer an invasion of Acarnania by the Ambracians and a body of Peloponnesian troops was repulsed ; and a large Peloponnesian fleet, which was to have joined in the attack on Acarnania, was twice defeated by Phormion in the mouth of the Corinthian Gulf. An expedition sent by the Athenians against the revolted Chalcidian towns was defeated with great loss.
In the preceding year (B.O. 430) the Athenians had concluded an alliance with Sitalces, king of the Odrysw, in Thrace, and Perdiccas, king of Macedon, on which occasion Sitalces had promised to aid the Athenians to subdue their revolted subjects in Chalcidice. He now collected an army of 150,000 men, with which he first invaded Macedonia, to revenge the breach of certain promises which Perdiccas had made to him the year before, and afterwards laid waste the territory of the Chalcidians and Bottimena, but he did not attempt to reduce any of the Greek cities. About the middle of this year Pericles died.
The invasion of Attica was repeated iu the next summer (423 H.e.); and immediately afterwards all Lesbos, except Methynme, revolted from the Athenians, who laid siege to Mytilene. The 3lytilemeans begged aid from Sparta, which was promised, and they were admitted into the Spartan alliance. In the same winter a body of the Platreans, amounting to 220, made their escape from the besieged city in the night, and took refuge in Athens.
In the summer of 427 B.C. the Peloponnesians again invaded Attica, while they sent a fleet of forty-two galleys, under Alcidas, to the relief of 3lytilene. Before the fleet arrived Mytilene had surrendered, and Alcidas, after a little delay, sailed home. In an assembly which was held at Athens to decide on the fate of the 3lytilenseans, it was resolved, at the instigation of Cleon, that all the adult citizens should be put to death, and the women and children made slaves ; but this barbarous decree was repealed the next day. [CtEors, in Biota. Div.] The land Lesbians (except those of Methymne) was seized, and divided among Athenian citizens, to whom the inhabitants paid a rent for the occupation of their former property. In the same summer the Platreana surrendered; they were massacred, and their city was given up to the Theban, who razed it to the ground.