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).
After these successful operations we reached a fortress called Thilutha, situated in the middle of the river, a place rising in a lofty peak and fortified by nature’s power as if by the hand of man. Since the difficulty and the height of the place made it impregnable, an attempt was made with friendly words (as was fitting) to induce the inhabitants to surrender; but they insisted that such defection then would be untimely. But they went so far as to reply, that as soon as the Romans by further advance had got possession of the interior, they also would go over to the victors, as appendages of the kingdom.
After this, as our ships went by under