Antoninus Pius (CE 138-161) replaced the wooden towers in the Odenwald with stone and reconstructed most of the forts in stone. The use of numeri was increased, and in CE 145-146 numeri Brittonum were building on the Neckar and in the Odenwald.

The sudden appearance of Britons is undoubtedly linked to the campaingn of Lollius Urbicus in northern Britain that extended Roman control north of Hadrian's Wall and led to the building of the Antonine Wall. The remaining fighting men of the conquered British tribes, organised into numeri, will have been deported to defend the frontier in Upper Germany. Unlike the auxiliary Cohorts and Alae, the numeri were not numbered. Units were distinguished by their ethnic name and a local name. In the case of the Britons, the local names all seem to be derived from the tributaries of the Main and the Neckar near which they were stationed.