While these things were being done by light, and openly, it was reported to the emperor [Julian], who was stretched thin by the diligence of his observation, that the legionary soldiers under orders to make “rabbit” tunnels had penetrated to the deepest parts of the foundations. Their paths underground were excavated and the beams hung up, and now, if he should direct it, they would breach.
And so, though most of the night had passed, a signal was given by a blast from the trumpet blowers to advance to the fight and they rushed to arms. As was planned, the fronts of the walls were attacked on two sides so that while the defenders ran around this way and that to ward off the danger, the nearby sound of the iron digging tools would not be audible and also, on the inside, there would be nothing preventing the bands of “rabbit” men from suddenly emerging.
When these things had been set up as it had been planned, and while the defenders were occupied, the mouths were opened up and Exsuperius, a soldier from the Victores unit, flew out; and then Magnus, a tribune, and Jovian the notary; and following them a whole courageous group. They first killed those whom they found in the building through which they had come out into the daylight; then they went forward on tiptoes and cut down all the watchmen, who, acting in the custom of their people, were singing praise for the justice and good fortune of their king with melodious voices.
Dumque haec luce agerentur ac palam, nuntiatur imperatori pervigili cura distento, legionarios milites, quibus cuniculorum erant fodinae mandatae, cavatis tramitibus subterraneis sublicibusque suspensis ima penetrasse fundamentorum, iam, si ipse disposuerit, evasuros.
cum itaque noctis plerumque processisset, aeneatorum accentu signo dato progrediendi ad pugnam, ad arma concursum est: et consulto murorum invaduntur utrimque frontes, ut, dum propulsaturi pericula defensores ultro citroque discurrunt, nec proxima fodientis audiretur ferri tinnitus nec quoquam intrinsecus obsistente cuniculariorum subito manus emergat.
quibus ita, ut convenerat, ordinatis et occupatis prohibitoribus patefactisque latebris evolat Exsuperius de Victorum numero miles, post quem Magnus tribunus et Iovianus notarius, quos audax multitudo secuta, his prius confossis, quos in aede, per quam in lucem prodierant, invenerunt, suspensis gradibus procedentes obtruncarunt vigiles omnes, ex usu moris gentici iustitiam felicitatemque regis sui canoris vocibus extollentes.
—Ammianus Marcellinus, Res Gestae 24.4.21–23
“Sappers” just doesn’t get across what an interesting Latin term this is.