It was a war of genocide waged against the ancient peoples of Scotland, which has largely been forgotten by history.

In the third century AD, the Roman Emperor Septimus Severus marched his legions north of Hadrian’s Wall and laid waste to the tribes of Caledonia, extending the Empire’s control all the way to the foothills of the Highlands.

And now people are being given the chance to follow in the footsteps of the imperial army as it made its way to the lands of Scotland, with a guided tour by the historian who recently researched the story behind the invasion.

The Emperor Severus embarked on his mission to pacify the north of Britain amid reports of a growing threat from the unconquered side of the wall.

A tribal confederation of the Maeatae and the Caledonians had formed an alliance to launch an assault on the south, and Severus left Rome with an army of 50,000 legionaries to meet the challenge.

It is possible he was influenced by desire to gain control over one of the few uncivilised parts of Europe within his reach, but he may also have been influenced by a prophecy that he would become a god if he conquered both North Britannia and the Parthian Empire to the east. Whatever the reason, he made his base at York before launching not one but two sustained military campaigns into ancient Scotland, giving orders to “kill everyone, even the unborn in the womb”.

Dr Simon Elliott, a trustee of the Council of British Archaeology, documented the campaigns in his last book “Septimius Severus in Scotland: the Northern Campaigns of the First Hammer of the Scots” and for the first time laid out the route taken by the legions.

Next year he plans to trace the path from York to Hadrian’s Wall and up to the Gask Ridge in Perthshire, where the Romans built a string of forts to keep a watch on the Highlands.

The tour will also visit Inveresk, East Lothian, where the legions halted and visit the remains of a supply depot on the River Tay at Crammond.

VisitScotland chief executive Malcolm Roughead has described it as a “welcome addition to Scotland’s rich and diverse mix of historical tours”.

Dr Elliot said: “I got the idea for the tour when I was actually doing the research for the Severus in Scotland book, visiting places like York, South Shields, Corbridge, Newstead, Inveresk, Cramond, Edinburgh, Carpow, the Gask Ridge and Ardoch.

“The story of his two huge campaigns north of the Border is astonishing, more Game of Thrones than Game of Thrones really, and linking these and other locations together for a week-long guide lectured tour is a brilliant way of telling it.

“People get to see the actual sites featured in the campaign, can understand how the geography and geology of the campaign theatre impacted upon it, and get a real sense of what Severus was trying to achieve, for good or ill.”

Severus, with his sons Geta and Caracalla, marched their army up the Roman road, which stretched to what is nowadays the Borders and drove the tribes back, before splitting the legions in two.  At some point, probably at South Queensferry, a bridge of 900 boats was built to allow the Caracalla to cross northwards, chasing the fleeing tribes who fought a guerilla campaign without resorting to a pitched battle they could not win.

The emperor then attacked from the south, subduing the local populace. He returned to York, but a second uprising forced him to send his men north again, prompting him to issue an order to his son to kill every man woman and child they encountered.

The resulting slaughter is believed to have led to a depopulation of the lowlands for a century, but Severus knew little of it. 

Already an old man when he launched the campaign, he died in 211 AD and his sons immediately left for Rome, leaving the Caledonian campaign as a footnote in history.

Dr Elliot said: “My objective is that those participating in the tour get the chance to learn every detail available about the Severan campaigns in Scotland, and the emperor himself, first hand as it were given the locations visited and my own expertise through researching and writing the book.

“The research into Severus naturally flowed from my PhD research which partly focused on the Classis Britannica Roman Navy in Britain.

“From there I wrote my first book, on the Classis Britannica itself called Sea Eagles of Empire.

“While researching that I came across one of the campaigns it had participated in, the Severan attempts to conquer Scotland. 

“The more I researched that the more I became hooked on these astonishing, audacious campaigns and decided to tell the story in book form for the first time.”