He now tried his fortune further in Thrace; and, singularly enough, he obtained recognition and support there not only from Teres the chief of the Thracian barbarians, the husband of his father's sister, and Barsabas, but also from the prudent Byzantines.
With Thracian support the so-called Philip invaded Macedonia, and, although he was defeated at first, he soon gained one victory over the Macedonian militia in the district of Odomantice beyond the Strymon, followed by a second on the west side of the river, which gave him possession of all Macedonia.

Apocryphal as his story sounded, and decidedly as it was established that the real Philip, the son of Perseus, had died when eighteen years of age at Alba, and that this man, so far from being a Macedonian prince, was Andriscus a fuller of Adramytium, yet the Macedonians were too much accustomed to the rule of a king not to be readily satisfied on the point of legitimacy and to return with pleasure into the old track.

Messengers arrived from the Thessalians, announcing that the pretender had advanced into their territory; the Roman commissioner Nasica, who, in the expectation that a word of earnest remonstrance would put an end to the foolish enterprise, had been sent by the senate to Macedonia without soldiers, was obliged to call out the Achaean and Pergamene troops and to protect Thessaly against the superior force by means of the Achaeans, as far as was practicable, till (605 ?) the praetor Juventius appeared with a legion.

The latter attacked the Macedonians with his small force; but he himself fell, his army was almost wholly destroyed, and the greater part of Thessaly fell into the power of the pseudo-Philip, who conducted his government there and in Macedonia with cruelty and arrogance.

At length a stronger Roman army under Quintus Caecilius Metellus appeared on the scene of conflict, and, supported by the Pergamene fleet, advanced into Macedonia.