Hellenistic armies in the context of "Seleucid army"

The Macedonian phalanx (Greek: Μακεδονική φάλαγξ) was an infantry formation developed by Philip II from the classical Greek phalanx, of which the main innovation was the use of the sarissa, a 6-metre pike. It was famously commanded by him during the rise of Macedon and by his son Alexander the Great during his conquest of the Achaemenid Empire and his other campaigns between 336 and 325 BC.

The Macedonian phalanx model then spread throughout the Hellenistic world, where it became the standard battle formation for pitched battles. During the Second Macedonian War (200–197 BC), Roman-Seleucid War (191–188 BC) and Third Macedonian War (171–168 BC) against the Roman Republic, the Hellenistic phalanx, both the Antigonid phalanx and the Seleucid phalanx, appeared less adaptable to changing conditions on the battlefield against the more flexible Roman legions.

The sarissa or sarisa was a long spear or pike about 5 to 7 meters (16 to 23 ft) in length. It was introduced by Philip II of Macedon and was used in his Macedonian phalanxes as a replacement for the earlier dory, which was considerably shorter. These longer spears improved the strength of the phalanx by extending the rows of overlapping weapons projecting towards the enemy. After the conquests of Alexander the Great, the sarissa was a mainstay during the Hellenistic era (4th–1st centuries BCE) by the Hellenistic armies of the diadochi Greek successor states of Alexander's empire, as well as some of their rivals.

The Antigonid Macedonian army was the army that evolved from the ancient Greek kingdom of Macedonia in the period when it was ruled by the Antigonid dynasty from 276 BC to 168 BC. It was seen as one of the principal Hellenistic fighting forces until its ultimate defeat at Roman hands at the Battle of Pydna in 168 BC. However, there was a brief resurgence in 150-148 during the revolt of Andriscus, a supposed heir to Perseus.

Starting as just a mere handful of mercenary troops under Antigonus Gonatas in the 270s BC, the Antigonid army eventually became the dominant force in Hellenistic Greece, fighting campaigns against Epirus, the Aetolian League, Sparta, Athens, Rhodes and Pergamon, not to mention the numerous Thracian and Celtic tribes that threatened Macedon from the north.

The Byzantine army was the primary military body of the Byzantine armed forces, serving alongside the Byzantine navy. A direct continuation of the Eastern Roman army, shaping and developing itself on the legacy of the late Hellenistic armies, it maintained a similar level of discipline, strategic prowess and organization. It was among the most effective armies of western Eurasia for much of the Middle Ages. Over time the cavalry arm became more prominent in the Byzantine army as the legion system disappeared in the early 7th century. Later reforms reflected some Germanic and Asian influences—rival forces frequently became sources of mercenary units, such as the Huns, Cumans, Alans and (following the Battle of Manzikert) Turks, meeting the Empire's demand for light cavalry mercenaries. Since much of the Byzantine military focused on the strategy and skill of generals utilizing militia troops, heavy infantry were recruited from Frankish and later Varangian mercenaries.

From the 6th to the 12th centuries, the Byzantine army was among the most powerful and effective military forces in the world – neither Middle Ages Europe nor (following its early successes) the fracturing Caliphate could match the strategies and the efficiency of the Byzantine army. Restricted to a largely defensive role in the 7th to mid-9th centuries, the Byzantines developed the theme system to counter the more powerful Caliphate. From the mid-9th century, however, they gradually went on the offensive, culminating in the great conquests of the 10th century under a series of soldier-emperors such as Nikephoros II Phokas, John Tzimiskes and Basil II. The army they led was less reliant on the militia of the themes; it was by now a largely professional force, with a strong and well-drilled infantry at its core and augmented by a revived heavy cavalry arm. With one of the most powerful economies in the world at the time, the Empire had the resources to put to the field a powerful host when needed, in order to reclaim its long-lost territories.

The Ptolemaic army was the army of the Ptolemaic Greek kings that ruled Egypt from 305 to 30 BC. Like most of the other armies of the Diadochi, it was very much Macedonian in style, with the use of the long pike (sarissa) in a deep phalanx formation. Despite the strength of the Ptolemaic army, evinced in 217 BC with the victory over the Seleucids at the Battle of Raphia, the Ptolemaic Kingdom itself fell into decline and by the time of Julius Caesar, it was but a mere client kingdom of the Roman Republic. The army by the time of Caesar’s campaigns in the eastern Mediterranean was a mere shadow of its former self: generally, a highly disorganized assemblage of mercenaries and other foreign troops.