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Large Roman fortress built by Caligula discovered near Amsterdam

A large Roman fortress has been discovered on the Dutch coast and is believed to have played a key role in the successful invasion of Britain in AD 43.

A Roman legion of “several thousand” combat-ready soldiers was stationed in Velsen, 20 miles from Amsterdam, on the banks of the Oer-IJ, a tributary of the Rhine, research suggests.

dr. Arjen Bosman, the archaeologist behind the findings, said the evidence pointed in the direction of Velsen Flevum in Latin, been the most northerly of the empire castra (fort) built to keep a Germanic tribe known as the Chauci at bay as the invading Roman forces prepared to cross from Boulogne in France to the southern beaches of England.

The fortified camp appears to have been founded by Emperor Caligula (12 to 41 AD) in preparation for his failed attempt to Britannia in about AD 40, but was then successfully developed and exploited by his successor, Claudius, before his own invasion in AD 43.

Bosman said: “We know for sure that Caligula was in the Netherlands, as there are markings on wooden wine barrels with the emperor’s initials burned in, suggesting that these came from the imperial court.

“What Caligula came to do was prepare to invade England – to achieve the same kind of military feat as Julius Caesar – but to invade and stay there. He couldn’t finish the job because he was killed in AD 41 and Claudius took over where he left off in AD 43.

It is believed that the Roman emperor Caligula founded the fortress near Velsen. Photo: Hulton Archive/Getty Images

“We have found wooden planks under the watchtower, or gate of the fort, and this is the phase just before the invasion of England. The wooden plank is dated to the winter of 42/43 AD. That’s a nice date. I jumped in the air when I heard it.”

Claudius’ invading forces, untouched by the Germanic tribes, landed in Kent, and by the summer of 43 AD the Emperor was confident enough to travel to Britain and enter. Camulodunum (Colchester) in triumph to receive the submission of 12 headmen.

Within three years, the Romans had claimed all of Britain as part of their empire.

Bosman said: “The main force came from Boulogne and Calais, but the northern flank of that attack had to be covered and was covered by the fort at Velsen. The Germanic threat appears several times in Roman literature.

“It was a warning system for the troops in France. It didn’t matter what the Germanic tribes put on the field, there was a legion there.”

The first evidence of a Roman fortress in Velsen, North Holland, was discovered in 1945 by schoolchildren who found pottery shards in an abandoned German anti-tank trench.

During the construction of the Velsertunnel, under the Nordzeekanaal, research was done in the 1950s and archaeological excavations took place in the 1960s and 1970s.

In 1997, Roman locks, a wall, and a gate were considered sufficient evidence by Bosman in three places for the area to become a state-protected archaeological site.

But at this stage, the Velsen camp, which was used between AD39 and AD47, was thought to be small.

This theory was supplemented by the 1972 discovery of an earlier fortress known as Velsen 1, which is believed to have been in use from AD 15 to AD 30. A thorough excavation of that site revealed that it had been abandoned after the revolt of the Frisians, the Germanic ethnic group native to the coastal areas of the Netherlands. Archaeologists discovered human remains in some former wells, a tactic used by retreating Romans to poison the water.

The existence of the two fortresses within a few hundred meters of each other had led researchers for decades to believe that they were probably both just castellum, small military camps of only one or two hectares.

It was not until November, by merging features of the later Veslen Fortress, noted in the 1960s and 1970s, but then not recognized as Roman, and taking into account its own archaeological finds over the past quarter century, that a new understanding was achieved.

“It is not one or two hectares like the first fort in Velsen, but certainly 11 hectares,” says Bosman. “We always thought it was the same size, but that’s not true. It was a legionary fortress and that is something completely different.”

Bosman added: “Until this year I wondered how many finds on Velsen 2, a lot of military equipment, a lot of weapons, long daggers, spears, much more than we found on Velsen 1.

“And we know that there was fighting on Velsen 1, and you can find weapons on a battlefield. The number of weapons on Velsen 2 can only be explained in the context of a legion. Several thousand men occupied this fortress.

“At 11 acres, this wouldn’t be a complete fortress for a full legion of 5,000 to 6,000 men, but we don’t know where it ends in the north and so it could have been bigger.”

Fortress Velsen 2 was abandoned in 47 AD after Claudius ordered all his troops to withdraw behind the Rhine. The Roman rule of Britain ended around AD 410 when the empire began to collapse in response to internal fighting and the increasing threats from Germanic tribes.