The Achaeans thus had war; and they had even actual allies, namely the Thebans and Boeotians and also the Chalcidians.  At the beginning of 608 the Achaeans advanced into Thessaly to reduce to obedience Heraclea near to Oeta, which, in accordance with the decree of the senate, had detached itself from the Achaean league.  The consul Lucius Mummius, whom the senate had resolved to send to Greece, had not yet arrived; accordingly Metellus undertook to protect Heraclea with the Macedonian legions.  When the advance of the Romans was announced to the Achaeo-Theban army, there was no more talk of fighting; they deliberated only how they might best succeed in reaching once more the secure Peloponnesus; in all haste the army made off, and did not even attempt to hold the position at Thermopylae.  But Metellus quickened the pursuit, and overtook and defeated the Greek army near Scarpheia in Locris.  The loss in prisoners and dead was considerable; Critolaus was never heard of after the battle.  The remains of the defeated army wandered about Greece in single troops, and everywhere sought admission in vain; the division of Patrae was destroyed in Phocis, the Arcadian select corps at Chaeronea; all northern Greece was evacuated, and only a small portion of the Achaean army and of the citizens of Thebes, who fled in a body, reached the Peloponnesus.  Metellus sought by the utmost moderation to induce the Greeks to abandon their senseless resistance, and gave orders, for example, that all the Thebans with a single exception, should be allowed their liberty; his well-meant endeavours were thwarted not by the energy of the people, but by the desperation of the leaders apprehensive for their own safety.  Diaeus, who after the fall of Critolaus had resumed the chief command, summoned all men capable of bearing arms to the isthmus, and ordered 12,000 slaves, natives of Greece, to be enrolled in the army; the rich were applied to for advances, and the ranks of the friends of peace, so far as they did not purchase their lives by bribing the ruling agents in this reign of terror, were thinned by bloody prosecutions.  The war accordingly was continued, and after the same style.  The Achaean vanguard, which, 4000 strong, was stationed under Alcamenes at Megara, dispersed as soon as it saw the Roman standards.  Metellus was just about to order an attack upon the main force on the isthmus, when the consul Lucius Mummius with a few attendants arrived at the Roman head-quarters and took the command.  Meanwhile the Achaeans, emboldened by a successful attack on the too incautious Roman outposts, offered battle to the Roman army, which was about twice as strong, at Leucopetra on the isthmus.  The Romans were not slow to accept it.  At the very first the Achaean horsemen broke off en masse before the Roman cavalry of six times their strength; the hoplites withstood the enemy till a flank attack by the Roman select corps brought confusion also into their ranks.  This terminated the resistance.  Diaeus fled to his home, put his wife to death, and took poison himself.  All the cities submitted without opposition; and even the impregnable Corinth, into which Mummius for three days hesitated to enter because he feared an ambush, was occupied by the Romans without a blow.