Why did the Roman army build the Antonine Wall in Scotland?

In 139 CE, the Roman emperor Antoninus Pius directed his general, Lollius Urbicus, to advance the Roman frontier in Britain northward from Hadrian’s Wall to the narrow isthmus between the River Clyde and the Firth of Forth.12

The construction of the Antonine Wall in 142 CE was part of a strategic effort to reoccupy Scotland and establish a new, shorter defensive line across the island. This location had previously been fortified by Gnaeus Julius Agricola during his earlier campaigns. By building this turf wall, the Roman army aimed to consolidate its control over the region and manage the frontier more effectively than the previous boundary. Despite these efforts, the wall did not secure long-term peace, and the Roman military eventually abandoned the site in the 160s CE, returning to the more established frontier of Hadrian’s Wall.231