The Romans, in search of iron, copper, precious metals, slaves, and crops, begin to expand into the Balkan Peninsula in the late third century BCE.

The tax burden on both rural and urban populations of the Hellenistic kingdoms rises as the constant military conflicts raise revenue needs.

The Persians, Parthians, and Bactrians meanwhile threaten from the east; and Roman expansionism in southern Italy and the western Mediterranean sets the stage for repeated clashes between Rome and various Hellenistic rulers.

Conflicts between the Roman Republic and the kingdom of Macedonia from 215 BCE cause increasing involvement by Rome in Greek affairs.

Antiochus III the Great, upon taking the Seleucid throne in 223 BCE, had set himself the task of restoring the lost imperial possessions of Seleucus I Nicator, which extended from Greco-Bactrian Kingdom in the east, the Hellespont in the north, and Syria in the south.

He has by 221 BCE reestablished Seleucid control over Media and Persia, which had been in rebellion.

The ambitious king turns his eyes toward Syria and Hellenistic Egypt.

Egypt has been significantly weakened by court intrigue and public unrest.

The rule of the newly inaugurated Ptolemy IV Philopator begins in 221 BCE with the murder of queen-mother Berenice II.

The young king quickly falls under the absolute influence of imperial courtiers.

His ministers use their absolute power in their own self-interest, to the people's great chagrin.

Antiochus seeks to take advantage of this chaotic situation.

After an invasion in 221 BCE fails to launch, he finally begins the Fourth Syrian War in 219 BCE.

He recaptures Seleucia Pieria as well as cities in Phoenicia, among them Tyre.

Rather than promptly invading Egypt, Antiochus waits in Phoenicia for over a year, consolidating his new territories and listening to diplomatic proposals from the Ptolemaic kingdom.

Ptolemy's minister Sosibius meanwhile begins recruiting and training an army.

The threat from Seleucid Syria is sufficiently grave that, for the first time under the Ptolemaic regime, Sosibus recruits not only from the local Greek population, as Hellenistic armies generally are, but also from the native Egyptians, enrolling at least thirty-thousand natives as phalangites.

This innovation pays off, but it will eventually have dire consequences for Ptolemaic stability.

Ptolemy, after intensive drilling of the reorganized Egyptian army, engages and defeats the long-delayed Antiochus in the summer of 217 BCE in the Battle of Raphia, the largest battle since the Battle of Ipsus over eighty years earlier.

Ptolemy's victory preserves his control over Coele-Syria, and the weak king declines to advance further into Antiochus' empire, even to retake Seleucia Pieria.

The Ptolemaic kingdom will continue to decline over the following years, suffering from economic problems and rebellion.

Antigonus III Doson, reviving the Hellenic Alliance as a confederacy of leagues with himself as president restores internal stability and reestablishes Macedon in a stronger position in Greece than it had enjoyed since the reign of Gonatas.

Antigonus defeats the Achaean League, together with Sparta, but allows a shadow of independence to what appears to be a large body constituting a kind of representative government.

The Social War, or the War of the Allies, fought from 220 BCE to 217 BCE between the Hellenic League under Philip V of Macedon and the Aetolian League, Sparta and Elis, is ended with the Peace of Naupactus.

As a result of the war, Philip V becomes the major military power in Greece.

Philip after 217 turns his attention westward towards the Roman Republic.

He takes Illyria on the westernmost part of the Balkan Peninsula, in 215 allies with Hannibal and Carthage against Rome, and even considers crossing the Adriatic Sea and invading Italy.

The Second Punic War, also referred to as the Hannibalic War (by the Romans), The War Against Hannibal, or "The Carthaginian War", begins in 218 BCE and involves combatants in the western and eastern Mediterranean.

This is the second major war between Carthage and the Roman Republic, with the crucial participation of Numidian-Berber armies and tribes on both sides.

The two states have three major conflicts against each other over the course of their existence.

They are called the "Punic Wars" because Rome's name for Carthaginians is Poeni, derived from Poenici (earlier form of Punici), a reference to the founding of Carthage by Phoenician settlers.

The war is to a considerable extent initiated by Rome, but is marked by Hannibal's surprising overland journey and his costly crossing of the Alps, followed by his reinforcement by Gallic allies and crushing victories over Roman armies in the battle of the Trebia and the giant ambush at Trasimene.

In the following year (216), Hannibal's army defeats the Romans again, this time in southern Italy at Cannae.

In consequence of these defeats, many Roman allies go over to Carthage, prolonging the war in Italy for over a decade.

Philip soon wins renown by supporting the Hellenic League in its war against Sparta, Aetolia, and Elis (219-217).

Philip of Macedon, having expelled the Aetolians from the Peloponnese, marches into Aetolia, sacking the federal capital of Thermum.

He makes peace in 217 with Aetolia.