The Veneti inhabited southern Armorica, along the Morbihan bay. They built their strongholds on coastal eminences, which were islands when the tide was in, and peninsulas when the tide was out. Their most notable city, and probably their capital, was Darioritum (now known as Gwened in Breton or Vannes in French), mentioned in Ptolemy's Geography.
The Veneti built their ships of oak with large transoms fixed by iron nails of a thumb's thickness. They navigated and powered their ships through the use of leather sails. This made their ships strong, sturdy and structurally sound, capable of withstanding the harsh conditions of the Atlantic.
Judging by Caesar's Bello Gallico the Veneti evidently had close relations with Iron Age Britain; he describes how the Veneti sail to Britain. They controlled the tin trade from mining in Cornwall and Devon. Caesar mentioned that they summoned military assistance from that island during the war of 56 BCE.
Julius Caesar's victories in the Gallic Wars, completed by 51 BCE, extended Rome's territory to the English Channel and the Rhine. Caesar became the first Roman general to cross both bodies of water when he built a bridge across the Rhine and conducted the first invasion of Britain.
Caesar reports in the Bellum Gallicum that in 57 BCE, the Gauls on the Atlantic coast, including the Veneti, were forced to submit to Caesar's authority as governor. They were obliged to sign treaties and yield hostages as a token of good faith. However, in 56 BCE, the Veneti captured some of Julius Caesar's officers while they were foraging within their legions, intent on using them as bargaining chips to secure the release of the hostages Caesar had forced them to give him. Angered by what he considered a breach of law, Caesar prepared for war.
Given the highly defensible nature of the Veneti strongholds, land attacks were frustrated by the incoming tide, and naval forces were left trapped on the rocks when the tide ebbed. Despite this, Caesar managed to engineer moles and raised siegeworks that provided his legions with a base of operations. However, once the Veneti were threatened in one stronghold, they used their fleet to evacuate to another stronghold, obliging the Romans to repeat the same engineering feat elsewhere.
Since the destruction of the enemy fleet was the only permanent way to end this problem, Caesar directed his men to build ships. However, his galleys were at a serious disadvantage compared to the far thicker Veneti ships. The thickness of their ships meant they were resistant to ramming, whilst their greater height meant they could shower the Roman ships with projectiles, and even command the wooden turrets which Caesar had added to his bulwarks. The Veneti manoeuvred so skilfully under sail that boarding was impossible. These factors, coupled with their intimate knowledge of the coast and tides, put the Romans at a disadvantage. However, Caesar's legate Decimus Junius Brutus Albinus was given command of the Roman fleet, and in a decisive battle, succeeded in destroying the Gaulish fleet in Quiberon Bay, with Caesar watching from the shore. Using long billhooks, the Romans struck at the enemy's halyards as they swept past (these must have been fastened out-board), having the effect of dropping the huge leathern mainsails to the deck, which crippled the vessel whether for sailing or rowing. The Romans were at last able to board, and the whole Veneti fleet fell into their hands.
The strongholds on the coast were now stormed and the nobles were slaughtered and the rest sold into slavery. This served as a lesson to the rest of the confederacy of the fate in store for those who dared to stand against Rome.