They are probably related to the AD 106 Campaign of Trajan which conquered the Nabataean kingdom and constituted the province of Arabia Petraea.
🐪 The trajectory indicated by these new camps suggests an expedition toward Dûmat al-Jandal and Sakaka in the Jawf region at the eastern extent of the Nabataean kingdom. Charloux and Loreto (Reference Charloux and Loreto2013) suggest the existence of a minor caravan route linking Bayir and Dûmat al-Jandal, which would mirror the route implied by the camps. The use of such a peripheral route could have been part of a strategy to bypass the more obvious route down the Wadi Sirhan, adding an element of surprise to any attack on the Jawf region, or as a flanking manoeuvre as part of a broader campaign, with a second force in the Wadi Sirhan possibly responsible for the camp built at Azraq.
The distance between the camps across barren terrain is arguably too far to be crossed by infantry in a day and supports the alternative that the camps were for mounted troops—perhaps with camels. Based on the models developed by Richardson (Reference Richardson2002) on Roman camp capacity, we conjecture that the western camp could have held two notional mounted cohorts, while the smaller central and western camps held a single mounted cohort.
https://www.cambridge.org/core/journals/antiquity/article/lost-campaign-new-evidence-of-roman-temporary-camps-in-northern-arabia/538421A1D1F89C6EA23F1B757D08CB91
📎 LiorLefineder