Snare

INSIDIA. – I. (from the Latin insidiae and insideo) is the deception secretly prepared against someone, and it is given various names according to the different purposes toward which it is directed: deceit, fraud, inducement to sin, defamation, injury, homicide, temptation; here it is considered insofar as it signifies deception aimed at disorienting the enemy, especially in wartime.

As early as his own time, Augustine maintained that waging war, even not openly but by means of stratagems, does not mean violating the virtue of justice; the sufficiently numerous examples in the Old Testament prove this doctrine, which was accepted not only by the Gentiles but also by the chosen people. God himself commanded Joshua to use stratagems against the inhabitants of the city of Ai (Jos., 8:2, 4, etc.). Therefore, a stratagem is not intrinsically dishonorable, although the means by which it is employed may be so—for example, when one lies or violates agreements: this is certainly forbidden, since it is contrary to charity when it is not also contrary to justice (Sum. Theol., 2ᵃ-2ᵃc, q. 40, 3 and q. 71, 3 ad 3).

It is nevertheless possible for the enemy himself to be deceived because something has been kept hidden from him (e.g., war plans or troop movements), or because he believes troop movements in one direction to be genuine, whereas they are feigned. Moreover, in modern international law, whether by custom or by express convention, it is customary to employ ruses, stratagems, ambushes, simulated retreats, and bivouac fires in order to induce the enemy to believe that enemy troops are encamped in a given place. In all these cases there is no violation either of justice or of charity, except apparently; for well-ordered charity begins with oneself. On the other hand, it is unlawful to use the enemy’s military uniform, to hoist the enemy’s war flag in the field, to demand surrender by deception, or to send weapons and military personnel toward the enemy’s battlefield under the insignia of the Red Cross.

Unfortunately, every war weakens the moral principles that should regulate relations even between enemies, nor do international laws and conventions suffice to eliminate this effect: for this reason it is easy to pass from simple ambushes to clear and open violations of laws, including natural law.