Res Gestae
Ammianus Marcellinus
Ammianus Marcellinus. Ammianus Marcellinus, with an English translation, Vols. I-III. Rolfe, John C., translator. Cambridge, MA; London: Harvard University Press; W. Heinemann, 1935-1940 (printing).
Then it was decided, after this course of events,
And at once, for fear that the ardour of the warriors might cool, light-armed troops were put into skiffs, and taking the course which offered the greatest secrecy, came upon the lurking-places of the Sarmatians; and the enemy were deceived as they suddenly came in sight, seeing their native boats and the manner of rowing of their own country.
But when from the glittering of the weapons afar off they perceived that what they feared was approaching, they took refuge in marshy places; but the soldiers, following them still more mercilessly, slew great numbers of them, and gained a victory in a place where it seemed impossible to keep a firm footing or venture upon any action.