The Battle of Koroneia (Latin: Proelium koroneia, Greek: μάχη τῆς Κοροναίας) was a decisive battle that took place during the Third Macedonian War between the Roman Republic and the Antigonid Kingdom of Macedon, fought near Lake Koroneia in Thessaloniki, Greece. The Macedonians, led by King Argeos II, attempted to encircle the main Roman army which was currently besieging Thessalonica. However, they were met by Galerius Aetius with just a single legion, who had fortified the western edge of the Mygdonia Valley. Assuming an easy victory and requiring the element of surprise, Argeos charged the Roman positions, however, Galerius's ingenuity and the flexibility of the legion proved decisive against the Macedonian phalanx.
Despite the small size of his force, Galerius's tactics and preparations allowed him to inflict far greater casualties upon the Macedonians and is seen as a masterpiece of defence-in-detail and single to double envelopment. Argeos II was captured by Roman cavalry, thus putting an end to the Third Macedonian War. Galerius's victory resulted in his first triumph and received widespread acclaim from across the Roman world.
Background[]
The Roman Republic and Antigonid dynasty of Macedon had been on uneasy terms for the best part of a century. During the regency of Aloeus Autokrator the Antigonids waged a highly successful war against the Republic, with the regent himself achieving a decisive victory at the Padus River. As a result, Illyria was to be considered a client kingdom of Macedon, much to the chagrin of the Republic. After the death of Aloeus, the Republic attempted again to exert influence upon the western Balkans, and without the energetic leadership of the old regent, the Antigonids failed to counter the Latin advance.
A second war was waged, much to the favour of Rome. The client kingdoms were partially annexed into Roman colonia, and the surviving Hellenic states on the Adriatic coast coming under partial Roman occupation. However, following this success, the Republic failed to capitalise upon their advances, instead focusing on internal squabbles amongst the senate and Gallic incursions into Italy. Under King Argeos I and his son, Euenus, the Antigonids managed to make headway in re-integrating many of the Greek states.