The 'Lost' Naval Commands of Late Rome

[Renatus]

Vegetius 1. 3 .3 has 'in agrariis '

Ah, so he does! Although the passage is about the problems of conscripting city dwellers rather than countrymen, so the general idea of being out in the fields, in an agricultural rather than urban setting, probably still stands.

Lewis & Short refers to 'agrariae stationes ' in Ammianus 14. 3 and defines the expression as 'outposts'. I don't doubt that the etymology derives from the notion that outposts would, by definition, be out in the country and remote from urban settlements. If Vegetius and Ammianus are indeed referring to outposts, I guess that that might justify agraria being defined as an outpost or 'a kind of military watch'.