The naval battle at Ecnomus between the Romans and Carthaginians sits at the top of the list of great sea battles of antiquity along with Salamis. Ecnomus was pivotal to Rome’s success in the first Punic War because it established Rome as a legitimate sea power, equal to the Carthaginians, and set the stage for the Roman invasion of Africa. Our best source of information about the battle comes from Polybius writing one hundred years after the event.
In 256 B.C. Rome assembled a large naval force for the purpose of defeating the Punic navy and opening the door to an invasion of Africa. The fleet supposedly included some 330 ships including troop transports, although there has been much debate about the accuracy of these numbers. The Carthaginian fleet was approximately equal to that of the Romans.
The Roman plan was to sail south from Messana round Cape Pachyrus and head west to Cape Ecnomus where they would rendezvous with Roman land forces encamped there. Then the fleet would proceed on to Africa. If the Punic fleet was encountered, the Romans planned to drive it out of their way.
The Carthaginians through their spy network were able to follow the Roman advance and arrange the battle on their schedule. Moreover the Carthaginians had spied on Roman maneuvers where the attack formation was rehearsed.
The diagram above shows the Roman attack “V” made up of force 1 and 2. Force 3 overlapped the "V" and completed the triangle formation. It was made up mainly of troop transports. Force 4 was an auxiliary battle fleet nicknamed “Triarii”.
The Punic fleet consisted of a long line stretched across the Roman front. The left flank of this line was pulled in at an oblique angle because of the nearby coastline.
The diagram shown above depicts the Punic battle plan. Hamilcar planned to collapse his center so his wings could attack the Roman fleet from the flanks. This is in fact what happened during the battle.
This diagram shows the progression of Hamilcar’s attack. He made the mistake of focusing his forces on the transports, Triarii, and the rear of force 1 and 2 as shown above. That allowed large segments of force 1 and 2 to wheel around and attack the Punic force from behind after they had disposed of the Punic center.
he above diagram depicts the way the Romans were able to achieve victory by a circular attack. Hamilcar lost 30 ships and had 64 taken, while Rome lost 24 ships.
One reason why this battle is interesting is that it anticipates the later military battles with Hannibal. The Romans always used massive forces to punch through the center of the enemy line, unlike the Carthaginians who preferred to let their center sag and set up an attack from the wings. Regarding the interesting use of the word "Triarii" which was the familiar designation for the third (and most experienced) line in the Roman army formation behind the Hastati and Principes, the term as used at Ecnomus likely refers to "third" line and has no relationship to the sailor's experience.