Origin of the limes

[D B Campbell]

When did the limes originate? I mean, when did the Roman start to think about a defensive strategy?

This is a huge question, Jona! Besides the fact that it presupposes a "Roman" strategy, rather than the personal inclinations of successive emperors, it also begs the question that Romans could differentiate between a "defensive" strategy and an "offensive" one.

Of course, the empire must have had a "limit" at any given time, but the real question is whether the Romans ever acknowledged that the limit was permanent. Hadrian is usually cited, because the erection of stone frontier walls seems to suggest this acknowledgement of a permanent limit; but remember, there were still Roman "outposts" beyond the walls. And, in any case, Antoninus Pius promptly extended the frontiers, as if to point out that Hadrian's limits were not his.

Another "given" is usually the Euphrates. But the case is far from clear-cut. The Parthians were usually keen on ensuring that the Romans did not overstep the mark, but the Romans, from Trajan's time anyway, were equally keen on showing that the Euphrates could be overstepped at will. Nevertheless, successive emperors seem to have been perfectly content to respect the status quo, provided Rome did not suffer any loss of face.

I'm not so sure that either watchtowers or stone foundations hold the key, though. Watchtowers were occasionally erected along roadways, so they cannot be used as proof of a frontier. (No, not even on the Gask Ridge, which is just another roadway.) And stone-built forts may indicate that their founder envisaged no further movement, only to be superceded by a successor who decided that there should be further movement. I'm also less than sure of geographical arguments based on whether one line is a "more scientific" frontier than another line, given the shockingly basic maps used by the Romans!

A huge question, and a fascinating one. Thanks for bringing it up, Jona!