Origin of the limes

[Praefectusclassis]

(Just following the notorious Wheeler again, who does have useful points) Defensive thinking might be inferred when it's actually mentioned. Wheeler points to Dio 52.27 and 31, which call for strong frontier defenses, and Strabo 6.4.2 and 17.3.25. A perceived necessity to control an area - via fortifications, patrols (see Hadrian's wall?) - might certainly indicate defensive preparations, no? Wheeler also states that the Augustus biography of Nicolaus (FrGrHist 2A.391) ephasizes defense. Other quotes: Herodian 2.11.5 and Dio 75.3.2 which calls Mesopotamia a probolos, bulwark.