The Roman senate had long been at one in the opinion that Macedonia must give up all her possessions abroad; accordingly, when the ambassadors of Philip appeared in Rome, they were simply asked whether they had full powers to renounce all Greece and in particular Corinth, Chalcis, and Demetrias, and when they said that they had not, the negotiations were immediately broken off, and it was resolved that the war should be prosecuted with vigour.

With the help of the tribunes of the people, the senate succeeded in preventing a change in the chief command--which had often proved so injurious--and in prolonging the command of Flamininus; he obtained considerable reinforcements, and the two former commanders-in-chief, Publius Galba and Publius Villius, were instructed to place themselves at his disposal.

Philip resolved once more to risk a pitched battle.
To secure Greece, where all the states except the Acarnanians and Boeotians were now in arms against him, the garrison of Corinth was augmented to 6000 men, while he himself, straining the last energies of exhausted Macedonia and enrolling children and old men in the ranks of the phalanx, brought into the field an army of about 26,000 men, of whom 16,000 were Macedonian -phalangitae-.
Philip Proceed to Thessaly Battle of Cynoscephalae Thus the fourth campaign, that of 557, began.

Flamininus despatched a part of the fleet against the Acarnanians, who were besieged in Leucas; in Greece proper he became by stratagem master of Thebes, the capital of Boeotia, in consequence of which the Boeotians were compelled to join at least nominally the alliance against Macedonia.
Content with having thus interrupted the communication between Corinth and Chalcis, he proceeded to the north, where alone a decisive blow could be struck.

The great difficulties of provisioning the army in a hostile and for the most part desolate country, which had often hampered its operations, were now to be obviated by the fleet accompanying the army along the coast and carrying after it supplies sent from Africa, Sicily, and Sardinia.