Declassified images from American Cold War spy satellites have revealed hundreds of lost Roman forts on the Eastern frontier of the empire.

Archaeologists found 396 unknown forts in present day Syria and Iraq, in a discovery which paints a new picture of life in the region between 145 to 305 AD.

Aerial surveys in the 1930s by Antoine Poidebard, the French archaeologist, had shown a line of forts running more than 600 miles along the eastern border of the Roman empire, leading experts to assume they had acted as a defensive barrier.

But the survey has shown hundreds more spread out across both sides of the border, suggesting they acted as staging posts, where travellers could rest, recuperate and get fresh camels.