The Greeks had planted their trading posts in Sicily, Iberia, Sardinia and Africa during the 11th century and 10thcentury BC. They were creating a trading monopoly. They established their colony in South Italy and Sicily or Magna Graecia. This intensified competition between the Etruscan and Carthage Italian cities and the Greeks with an aim of controlling the Western Mediterranean Sea in order to control sea-borne trade.
The Greeks or Phocean from the Asian Minor or the Modern Turkey established a Massilia colony around 600 BC. This had become a strong trading center. It was a major rival to Carthage for Spanish markets as well as the tin trade via Gaul. In 546 BC, the Phocaea city fell to the Cyrus of the Great Persia. Consequently, most Phocaeans relocated to Alalia within Corsica. Due to the fear that their North Italy colonies and Sardinia would be threatened by the Greeks, the Carthaginians and Etruscans joined their forces in order to face the Greeks together.
Generally, the actual immediate cause of this battle was the presence of the Greeks and the establishment of a colony which led to increased trade and piracy among other conflicts between the Phoenicians, Etruscans and other groups in the regions that were competing to take control of the seaborne trade.
A common assumption is that there were 60 Pentekonters or 48 oars ships and 2 steering rudders instead of trireme that would become famous during the Battle of Salamis. The allied fleet was larger than that of the Greeks. However, the Greeks forces managed to drive allied fleets away. Nevertheless, almost two-third of the Greek fleet was lost during the battle. The Greeks left Corsica immediately when they realized that they did not have the ability to withstand an attack or fight such a battle again. There are sketchy details of this battle and it is not known how much the Etruscan and Carthaginians lost.
There are historians who consider the defeat of the Greeks and absence of Greek traders in the region, especially Gibraltar Strait, as what made Tartessian Civilization collapse in the southern part of Spain and the presence of the Punic remain undisturbed. Corsica became a territory of the Etruscans while Sardinia remained with the Carthaginians. Carthage had to fight two additional naval battles against Massalia and it lost both. However, it managed to close the Gibraltar Strait to Greek shipping. This enabled it to contain the expansion of Greek in Spain. The Etruscans attempted to conquer areas of Greek in Italy but Cumae, the Greek city, opposed them. The expansion of Carthaginian in Sicily was opposed by Syracuse. This set a stage on which Sicilian Wars were fought between the Greeks and the Carthage. Carthage spent many years following this war trying to improve its finances as well as expanding empires into Hispania or Iberia. Generally, the Battle of Alalia had expansive and long term effects.