The same years which brought to a successful issue the long struggle
with Persia witnessed a renewal of those internal conflicts by which
the energies of Greece were finally exhausted, leaving her an easy
prey to the arms of Macedon. The guilt of renewing these suicidal
quarrels lies with the Spartans, who had long been nursing their
grudge against Athens, and were waiting for the opportunity to inflict
on her a fatal blow. Fifteen years [Footnote: B.C. 464. ] after the
battle of Plataea they seized the occasion when the Athenians were
engaged with a large part of their forces in carrying on operations
against the revolted island of Thasos to prepare an invasion of
Attica. But at the very moment when they were meditating this act of
perfidy a double disaster fell upon them at home, demanding all their
exertions to save them from ruin. Sparta was levelled to the ground by
a terrible earthquake, in which twenty thousand of her citizens
perished; and in the midst of the panic caused by this awful calamity
the Helots rose in arms against their oppressors, and forming an
alliance with the Messenian subjects of Sparta, entrenched themselves
in a strong position on Mount Ithome. Here they maintained themselves
for two years, defying all the efforts of the Spartans to drive them
from their stronghold. In spite of their recent treachery, the
Spartans were not ashamed to apply to Athens for help: and chiefly
through the influence of Cimon, whose laurels from the Eurymedon were
still fresh, four thousand Athenian hoplites [Footnote: Heavy-armed
foot-soldiers.] were sent under his command to aid in dislodging the
Helots. The Athenians were famous for their skill in attacking
fortified places; but on this occasion they were unsuccessful, and the
Spartans, whose evil conscience made them prone to suspicion, at once
began to doubt the honesty of their intentions, and dismissed them
with scant ceremony. This unfriendly act helped to embitter the
relations between the two leading cities of Greece; and two years