Thus in reality all political, commercial, and moral motives concurred in inducing Rome to undertake the second war against Philip - one of the most righteous, which the city ever waged. It greatly redounds to the honour of the senate, that it immediately resolved on its course and did not allow itself to be deterred from making the necessary preparations either by the exhaustion of the state or by the unpopularity of such a declaration of war. The propraetor Marcus Valerius Laevinus made his appearance as early as 553 with the Sicilian fleet of 38 sail in the eastern waters. The government, however, were at a loss to discover an ostensible pretext for the war; a pretext which they needed in order to satisfy the people, even although they had not been far too sagacious to undervalue, as was the manner of Philip, the importance of assigning a legitimate ground for hostilities. The support, which Philip was alleged to have granted to the Carthaginians after the peace with Rome, manifestly could not be proved. The Roman subjects, indeed, in the province of Illyria had for a considerable time complained of the Macedonian encroachments. In 551 a Roman envoy at the head of the Illyrian levy had driven Philip's troops from the Illyrian territory; and the senate had accordingly declared to the king's envoys in 552, that if he sought war, he would find it sooner than was agreeable to him. But these encroachments were simply the ordinary outrages which Philip practised towards his neighbours; a negotiation regarding them at the present moment would have led to his humbling himself and offering satisfaction, but not to war. With all the belligerent powers in the east the Roman community was nominally in friendly relations, and might have granted them aid in repelling Philip's attack. But Rhodes and Pergamus, which naturally did not fail to request Roman aid, were formally the aggressors; and although Alexandrian ambassadors besought the Roman senate to undertake the guardianship of the boy king, Egypt appears to have been by no means eager to invoke the direct intervention of the Romans, which would put an end to her difficulties for the moment, but would at the same time open up the eastern sea to the great western power. Aid to Egypt, moreover, must have been in the first instance rendered in Syria, and would have entangled Rome simultaneously in a war with Asia and with Macedonia; which the Romans were naturally the more desirous to avoid, as they were firmly resolved not to intermeddle at least in Asiatic affairs. No course was left but to despatch in the meantime an embassy to the east for the purpose, first, of obtaining - what was not in the circumstances difficult - the sanction of Egypt to the interference of the Romans in the affairs of Greece; secondly, of pacifying king Antiochus by abandoning Syria to him; and, lastly, of accelerating as much as possible a breach with Philip and promoting a coalition of the minor Graeco-Asiatic states against him (end of 553). At Alexandria they had no difficulty in accomplishing their object; the court had no choice, and was obliged gratefully to receive Marcus Aemilius Lepidus, whom the senate had despatched as "guardian of the king" to uphold his interests, so far as that could be done without an actual intervention. Antiochus did not break off his alliance with Philip, nor did he give to the Romans the definite explanations which they desired; in other respects, however - whether from remissness, or influenced by the declarations of the Romans that they did not wish to interfere in Syria - he pursued his schemes in that direction and left things in Greece and Asia Minor to take their course.
Meanwhile, the spring of 554 had arrived, and the war had recommenced. Philip first threw himself once more upon Thrace, where he occupied all the places on the coast, in particular Maronea, Aenus, Elaeus, and Sestus; he wished to have his European possessions secured against the risk of a Roman landing. He then attacked Abydus on the Asiatic coast, the acquisition of which could not but be an object of importance to him, for the possession of Sestus and Abydus would bring him into closer connection with his ally Antiochus, and he would no longer need to be apprehensive lest the fleet of the allies might intercept him in crossing to or from Asia Minor. That fleet commanded the Aegean Sea after the withdrawal of the weaker Macedonian squadron: Philip confined his operations by sea to maintaining garrisons on three of the Cyclades, Andros, Cythnos, and Paros, and fitting out privateers. The Rhodians proceeded to Chios, and thence to Tenedos, where Attalus, who had passed the winter at Aegina and had spent his time in listening to the declamations of the Athenians, joined them with his squadron. The allies might probably have arrived in time to help the Abydenes, who heroically defended themselves; but they stirred not, and so at length the city surrendered, after almost all who were capable of bearing arms had fallen in the struggle before the walls. After the capitulation a large portion of the inhabitants fell by their own hand - the mercy of the victor consisted in allowing the Abydenes a term of three days to die voluntarily. Here, in the camp before Abydus. the Roman embassy, which after the termination of its business in Syria and Egypt had visited and dealt with the minor Greek states, met with the king, and submitted the proposals which it had been charged to make by the senate, viz. that the king should wage no aggressive war against any Greek state, should restore the possessions which he had wrested from Ptolemy, and should consent to an arbitration regarding the injury inflicted on the Pergamenes and Rhodians. The object of the senate, which sought to provoke the king to a formal declaration of war, was not gained; the Roman ambassador, Marcus Aemilius Lepidus, obtained from the king nothing but the polite reply that he would excuse what the envoy had said because he was young, handsome, and a Roman.
Meanwhile, however, the occasion for declaring war, which Rome desired, had been furnished from another quarter. The Athenians in their silly and cruel vanity had put to death two unfortunate Acarnanians, because these had accidentally strayed into their mysteries. When the Acarnanians, who were naturally indignant, asked Philip to procure them satisfaction, he could not refuse the just request of his most faithful allies, and he allowed them to levy men in Macedonia and, with these and their own troops, to invade Attica without a formal declaration of war. This, it is true, was no war in the proper sense of the term; and, besides, the leader of the Macedonian band, Nicanor, immediately gave orders to his troops to retreat, when the Roman envoys, who were at Athens at the time, used threatening language (in the end of 553). But it was too late. An Athenian embassy was sent to Rome to report the attack made by Philip on an ancient ally of the Romans; and, from the way in which the senate received it, Philip saw clearly what awaited him; so that he at once, in the very spring of 554, directed Philocles, his general in Greece, to lay waste the Attic territory and to reduce the city to extremities.
The senate now had what they wanted; and in the summer of 554 they were able to propose to the comitia a declaration of war "on account of an attack on a state in alliance with Rome". It was rejected on the first occasion almost unanimously: foolish or evil-disposed tribunes of the people complained of the senate, which would allow the citizens no rest; but the war was necessary and, in strictness, was already begun, so that the senate could not possibly recede. The burgesses were induced to yield by representations and concessions. It is remarkable that these concessions were made mainly at the expense of the allies. The garrisons of Gaul, Lower Italy, Sicily, and Sardinia, amounting in all to 20,000 men, were exclusively taken from the allied contingents that were in active service - quite contrary to the former principles of the Romans. All the burgess troops, on the other hand, that had continued under arms from the Hannibalic war, were discharged; volunteers alone, it was alleged, were to be enrolled for the Macedonian war, but they were, as was afterwards found, for the most part forced volunteers - a fact which in the autumn of 555 called forth a dangerous military revolt in the camp of Apollonia. Six legions were formed of the men newly called out; of these two remained in Rome and two in Etruria, and only two embarked at Brundisium for Macedonia, led by the consul Publius Sulpicius Galba. Thus it was once more clearly demonstrated, that the sovereign burgess assemblies, with their shortsighted resolutions dependent often on mere accident, were no longer at all fitted to deal with the complicated and difficult relations into which Rome was drawn by her victories; and that their mischievous intervention in the working of the state machine led to dangerous modifications of the measures which in a military point of were necessary, and to the still more dangerous course of treating the Latin allies as inferiors.