His most successful campaign was that in the Chersonesus, which proved the salvation of the Greeks residing there: for he not only settled a thousand colonists there, and thus increased the available force of the cities, but built a continuous line of fortifications reaching across the isthmus from one sea to the other, by which he shut off the Thracians, who had previously ravaged the peninsula, and put an end to a constant and harassing border warfare to which the settlers were exposed, as they had for neighbors tribes of wild plundering barbarians.
But that by which he obtained most glory and renown was when he started from Pegae, in the Megarian territory, and sailed round the Peloponnesus with a fleet of a hundred triremes; for he not only laid waste much of the country near the coast, as Tolmides had previously done, but he proceeded far inland, away from his ships, leading the troops who were on board, and terrified the inhabitants so much that they shut themselves up in their strongholds. The men of Sicyon alone ventured to meet him at Nemea, and them he overthrew in a pitched battle, and erected a trophy. Next he took on board troops from the friendly district of Achaia, and, crossing over to the opposite side of the Corinthian Gulf, coasted along past the mouth of the river Achelous, overran Acarnania, drove the people of Oeneadae to the shelter of their city walls, and after ravaging the country returned home, having made himself a terror to his enemies, and done good service to Athens; for not the least casualty, even by accident, befell the troops under his command.
When he sailed into the Black Sea with a great and splendidly equipped fleet, he assisted the Greek cities there, and treated them with consideration, and showed the neighboring savage tribes and their chiefs the greatness of his force, and his confidence in his power, by sailing where he pleased, and taking complete control over that sea. He left at Sinope thirteen ships, and a land force under the command of Lamachus, to act against Timesileon, who had made himself despot of that city. When he and his party were driven out, Pericles passed a decree that six hundred Athenian volunteers should sail to Sinope, and become citizens there, receiving the houses and lands which had formerly been in the possession of the despot and his party. But in other cases he would not agree to the impulsive proposals of the Athenians, and he opposed them when, elated by their power and good fortune, they talked of recovering Egypt and attacking the seaboard of the Persian empire. Many, too, were inflamed with that ill-starred notion of an attempt on Sicily, which was afterward blown into a flame by Alcibiades and other orators. Some even dreamed of the conquest of Etruria and Carthage, in consequence of the greatness which the Athenian empire had already reached, and the full tide of success which seemed to attend it.
Pericles, however, restrained these outbursts, and would not allow the people to meddle with foreign states, but used the power of Athens chiefly to preserve and guard her already existing empire, thinking it to be of paramount importance to oppose the Lacedaemonians, a task to which he bent all his energies, as is proved by many of his acts, especially in connection with the Sacred War. In this war the Lacedaemonians sent a force to Delphi, and made the Phocians, who held it, give it up to the people of Delphi: but as soon as they were gone Pericles made an expedition into the country, and restored the temple to the Phocians; and as the Lacedaemonians had scratched the oracle which the Delphians had given them, on the forehead of the brazen wolf there, Pericles got a response from the oracle for the Athenians, and carved it on the right side of the same wolf.
Events proved that Pericles was right in confining the Athenian empire to Greece. First of all Euboea revolted, and he was obliged to lead an army to subdue that island. Shortly after this, news came that the Megarians had become hostile, and that an army, under the command of Plistoanax, king of the Lacedaemonians, was menacing the frontier of Attica. Pericles now in all haste withdrew his troops from Euboea, to meet the invader. He did not venture on an engagement with the numerous and warlike forces of the enemy, although repeatedly invited by them to fight: but, observing that Plistoanax was a very young man, and entirely under the influence of Cleandrides, whom the ephors had sent to act as his tutor and counsellor because of his tender years, he opened secret negotiations with the latter, who at once, for a bribe, agreed to withdraw the Peloponnesians from Attica. When their army returned and dispersed, the Lacedaemonians were so incensed that they imposed a fine on their king, and condemned Cleandrides, who fled the country, to be put to death. This Cleandrides was the father of Gylippus, who caused the ruin of the Athenian expedition in Sicily. Avarice seems to have been hereditary in the family, for Gylippus himself, after brilliant exploits in war, was convicted of taking bribes, and banished from Sparta in disgrace.
When Pericles submitted the accounts of the campaign to the people, there was an item of ten talents, "for a necessary purpose," which the people passed without any questioning, or any curiosity to learn the secret. Some historians, among whom is Theophrastus the philosopher, say that Pericles sent ten talents annually to Sparta, by means of which he bribed the chief magistrates to defer the war, thus not buying peace, but time to make preparations for a better defence. He immediately turned his attention to the insurgents in Euboea, and proceeding thither with a fleet of fifty sail, and five thousand heavy armed troops, he reduced their cities to submission. He banished from Chalcis the "equestrian order," as it was called, consisting of men of wealth and station; and he drove all the inhabitants of Hestiaea out of their country, replacing them by Athenian settlers. He treated these people with this pitiless severity, because they had captured an Athenian ship, and put its crew to the sword. After this, as the Athenians and Lacedaemonians made a truce for thirty years, Pericles decreed the expedition against Samos, on the pretext that they had disregarded the commands of the Athenians to cease from their war with the Milesians.
Pericles is accused of going to war with Samos to save the Milesians. These states were at war about the possession of the city of Priene, and the Samians, who were victorious, would not lay down their arms and allow the Athenians to settle the matter by arbitration, as they ordered them to do. For this reason Pericles proceeded to Samos, put an end to the oligarchical form of government there, and sent fifty hostages and as many children to Lemnos, to insure the good behavior of the leading men. It is said that each of these hostages offered him a talent for his own freedom, and that much more was offered by that party which was loath to see a democracy established in the city. Besides all this, Pissuthnes the Persian, who had a liking for the Samians, sent and offered him ten thousand pieces of gold if he would spare the city. Pericles, however, took none of these bribes, but dealt with Samos as he had previously determined, and returned to Athens. The Samians now at once revolted, as Pissuthnes managed to get them back their hostages, and furnished them with the means of carrying on the war. Pericles now made a second expedition against them, and found them in no mind to submit quietly, but determined to dispute the empire of the seas with the Athenians. Pericles gained a signal victory over them in a sea-fight off the Goats' Island, beating a fleet of seventy ships with only forty-four, twenty of which were transports.
Simultaneously with his victory and the flight of the enemy he obtained command of the harbor of Samos, and besieged the Samians in their city. They, in spite of their defeat, still possessed courage enough to sally out and fight a battle under the walls; but soon a larger force arrived from Athens, and the Samians were completely blockaded.
Pericles now with sixty ships sailed out of the Archipelago into the Mediterranean, according to the most current report intending to meet the Phoenician fleet which was coming to help the Samians, but, according to Stesimbrotus, with the intention of attacking Cyprus, which seems improbable. Whatever his intention may have been, his expedition was a failure, for Melissus, the son of Ithagenes, a man of culture, who was then in command of the Samian forces, conceiving a contempt for the small force of the Athenians and the want of experience of their leaders after Pericles' departure, persuaded his countrymen to attack them. In the battle the Samians proved victorious, taking many Athenians prisoners, and destroying many of their ships. By this victory they obtained command of the sea, and were able to supply themselves with more warlike stores than they had possessed before. Aristotle even says that Pericles himself was before this beaten by Melissus in a sea-fight. The Samians branded the figure of an owl on the foreheads of their Athenian prisoners, to revenge themselves for the branding of their own prisoners by the Athenians with the figure of a samaina. This is a ship having a beak turned up like a swine's snout, but with a roomy hull, so as both to carry a large cargo and sail fast. This class of vessel is called samaina because it was first built at Samos by Polycrates, the despot of that island.
When Pericles heard of the disaster which had befallen his army, he returned in all haste to assist them. He beat Melissus, who came out to meet him, and, after putting the enemy to rout, at once built a wall round their city, preferring to reduce it by blockade to risking the lives of his countrymen in an assault. In the ninth month of the siege the Samians surrendered. Pericles demolished their walls, confiscated their fleet, and imposed a heavy fine upon them, some part of which was paid at once by the Samians, who gave hostages for the payment of the remainder at fixed periods.