The Law of Nations or the Principles of Natural Law (1758)Emmerich de Vattel Of Faith Between Enemies, — of Stratagems, Artifices in War, Spies, and Some Other Practices§ 174. Faith to be sacred between enemies.§ 175. What treaties are to be observed between enemies.§ 176. On what occasions they may be broken.§ 177. Of lies.§ 178. Stratagems and artifices in war.§ 179. Spies.§ 180. Clandestine seduction of the enemy's people.§ 181. Whether the offers of a traitor may be accepted.§ 182. Deceitful intelligence.
     1.    De salute ceriatum est.
     2.    Histoire de Guillaume III tom. ii. p.
     3.    Falsiloquium, false speaking, untruth, falsehood.
     4.    There was a time when those who were taken in attempting to surprise a town, were put to death. In 1597, prince Maurice attempted to take Venloo by surprise: the attempt failed; and some of his men, being made prisoners on the occasion, "were condemned to death, — the mutual consent of the parties having introduced that new rule, in order to obviate dangers of this kind." (Grotius Hist. of the Disturb, in the Netherlands.) Since that time, the rule has been changed: at present, military men who attempt to surprise a town in time of open war, are not, in case of being taken, treated in a different manner from other prisoners: and this custom is more consonant to reason and humanity. Nevertheless, if they were in disguise, or had employed treachery, they would be treated as spies; and this is, perhaps, what Grotius means; for I do not, in any other instance, find that such severity was used towards troops who were simply come to surprise a town in the silence of the night. It would be quite another affair, if such an attempt were made in time of profound peace; and the Savoyards, who were taken in the escalade of Geneva, deserved the punishment of death which was inflicted on them.
     5.    Mémoires de Feuquléres, tom. iii. p. 87.
     6.    This was the practice of the ancient Gauls. See Livy. — It is said of Achilles, that he was for fighting openly, and not of a disposition to conceal himself in the famous wooden horse, which proved fatal to the Trojans: — Ille non, inclosus equo Minervæ Sacra mentito, male feriatos Troas, et lætam Priami choreis Falleret aulam; Sed palam captis gravis. Hor. lib. iv. od. 6
     7.    Virg. æn. ii. 390. § Tit Liv. lib. xlii. cap. 47
     8.    Xenophon very properly expresses the reasons which render treachery detestable, and which authorize us to repress it by other means than open force. "Treachery," says he, "is more dreadful than open war, in proportion as it is more difficult to guard against clandestine plots than against an open attack: it is also more odious, because men engaged in overt hostilities may again treat together, and come to a sincere reconciliation; whereas nobody can venture to treat with or repose any confidence in a man whom he has once found guilty of treachery." — Hist. Graw. lib. ii. cap. 3.
     9.    Viriati etiam cædes duplicem perdiæ accusationem recepit, in amicis, quod eorum manibus interemptus est, in Q. Servilio Caepione consule, qula is sceleris hujus, auctor, impunita te promissa, full, victoriamque non meruit sed emit. — Lib. ix. cap. 6. — Although this instance seems to belong to another head (that of assassination), I nevertheless quote it here, because it does not appear, from other authors, that Cæpio had induced Viratus's soldiers to assassinate him. Among others, see Eutropius, lib. vi. cap. 8.
   10.    Quæ victoria, qula empta erat, a senatu non probata. Auctor de Viris Illust. cap. 71.
   11.    Transfugam jure belli recipimus. Digest 1. xli. tit. 1, de adquir. Rer. Dom. leg. 51.
   12.    Eâdem fide indicatum Pyrrho regi medicum vitæ ejus insidiantem; eâdem Faliscis vinctum traditum proditorem liberorum regis. Tit. Liv. lib. xlii. cap. 47
   13.    When the duke of Parma was engaged in the siege of Bergen-op-zoom, two Spanish prisoners, who were confined in a fort near the town, attempted to gain over a tavern-keeper, and an English soldier, to betray that fort to the duke. These men, having acquainted the governor with the circumstance, received orders from him to feign acquiescence; and, accordingly, having made all their arrangements with the duke of Parma for the surprisal of the fort, they gave notice of every particular to the governor. He, in consequence, kept himself prepared to give a proper reception to the Spaniards, who fell into the snare, and lost near three thousand men on the occasion. — Grotius, Hist, of the disturb, in the Netherlands, book i.