The Syrio-Egyptian negotiations collapse in 218 BCE and Antiochus renews his advance, overrunning Ptolemy's forward defenses.

The Seleucids now hold Coele Syria (Lebanon), Phoenicia, and Palestine.

Hannibal departs with his army from New Carthage (Cartagena, Spain) northwards along the coast in late spring of 218 BCE.

Excluding the forces in Africa, the Carthaginian army in Iberia, totaled, according to Polybius, ninety thousand infantry, twelve thousand cavalry and an unknown number of war elephants: it is thus one of the largest in the Hellenistic world and equal in numbers to any that the Romans have yet fielded.

Rome, probably acting on a combination of aristocratic ambitions, growing commercial interests, agitation by its ally Massilia, and fear of Carthage itself, declares war in the spring of 218.

The region of Piacenza is the main Italian gateway to the Alps, being also the confluence of the River Trebbia, draining the northern Apennines, and the Po, the major waterway of northern Italy, draining to the east.

The right bank of the Po River between the Trebbia River and the Taro River is occupied by the Ananes or Anamari, a tribe of Cisalpine Gauls.

Before then, says Polybius, "These plains were anciently inhabited by Etruscans", before the Gauls took the entire Po valley from them.

Although Polybius says the Etruscans were expelled, he meant perhaps selectively, as Etruscan culture had continued in the area until assimilated to the Roman.

The Romans had planned to construct Piacenza and Cremona as Roman military colonies after the successful conclusion of the latest war with the Gauls ending in 219 BCE.

The Senate, declaring war on Carthage in the spring of 218 BCE, decides to accelerate the foundation and gives the colonists thirty days to appear on the sites to receive their lands.

They are each to be settled by six thousand Roman citizens but the cities are to receive Latin Rights; that is, they are to have the same legal status as the many colonies that had been co-founded by Rome and towns of Latium.

The reaction of the Gauls in the region is swift; they drive the colonists off the lands.

Taking refuge in Mutina, the latter send for military assistance.

A small force under Lucius Manlius is prevented from reaching the area.

The Senate now sends two legions under Gaius Atelius.

Collecting Manlius and the colonists, they descend on Cremona and Piacenza and successfully place castra there of 480 m2 (0.12 acre) to support the building of the city.

What is today the Mediterranean port city of Tarragona, about fifty miles (eighty kilometers) southwest of Barcelona, has in the fifth through third centuries been settled by Iberians who have commercial contacts with the Greeks and Phoenicians who have settled on the coast.

The Iberian colonies are present particularly in the valley of Ebro.

The sources referring to the presence of Iberians in Tarraco are ambiguous.

Livy mentions a oppidum parvum (small colony) called Cissis, Polybius names a polis as Kissa.

Shortly after the arrival of Gnaeus Cornelius Scipio Calvus to Empúries (Emporion) in 218 BCE, in the Second Punic War, Tarraco is mentioned for first time.

Livy writes that the Romans conquered a field of Punic supplies for the troops of Hannibal near Cissis and took the city.

A short time later, the Romans were attacked "not far from Tarraco" (haud procul Tarracone), but it remains unclear whether Cissis and Tarraco was the same city.

Hannibal, planning to win the war with Rome by a surprise invasion of Italy from the north, makes his younger brother Hasdrubal commander in Spain, crosses the Pyrenees and southern Gaul, and then marches up the Rhône River.

Although impeded by early snows and the presence of eighty cumbersome elephants in his baggage train, Hannibal unexpectedly crosses the Alps, probably somewhere between the Little St. Bernard and Mt.

Genevre passes, into the Po Valley in the autumn of 218.

Once in the Po Valley, Hannibal recruits the Gauls, recently defeated by Rome between 225 and 220.

Piacenza must have been walled immediately, as the walls are in place when the Battle of the Trebbia is fought around the city in December.

There is no evidence either textual or archaeological of a prior settlement on that exact location; however, the site would have been obliterated by construction.

Piacenza, the fifty-third colony to be placed by Rome since its foundation, is the first among the Gauls of the Po valley.

Hannibal destroys Turin (founded by the Taurini and hence at first called Taurasia) in 218.

Hannibal routs the Romans again, late in 218 BCE, at the Trebia River.

Antiochus gives up all his conquests of the Fourth Syrian War in the peace that settles it, except the city of Seleucia-in-Pieria.

Ptolemy's new army (numbering seventy-five thousand) meets the Seleucid forces (sixty-eight thousand strong) near Raphia in southern Palestine in the spring of 217, however, and with the help of the Egyptian phalanx, Ptolemy is victorious.

The battle is notable for the fact that large numbers of native Egyptian soldiers have for the first time fought alongside the Macedonian and Greek contingents.

The Egyptian king, although holding the initiative, negotiates a peace on Sosibius' advice, and the Seleucid army withdraws from Coele Syria.