The Tin Can Ruse: Lawful Deception or Prohibited Treachery?

The law of armed conflict has always drawn an uncomfortable line between cunning and criminality. Commanders who deceive the enemy are celebrated; those who betray a protected confidence face prosecution. The difference, as modern codification encodes it, turns on a deceptively simple question: did the ruse invite reliance on a legal protection, or merely exploit the enemy’s ordinary situational expectations?

A trench anecdote from the Western Front—perhaps apocryphal, but certainly instructive—throws that distinction into sharp relief across more than a century of legal development.

The Anecdote and Its Evidential Limits

The story, attributed variably to British or Canadian troops on the Western Front, runs as follows. Soldiers in Allied trenches began lobbing tins of meat into German positions. The Germans, rather than treating the incoming objects as threats, retrieved and consumed the contents. Over time, the tins became associated not with danger but with an unexpected windfall, food thrown across no man’s land by an enemy whose motives were unclear but whose deliveries were welcome. Reportedly, the Germans grew so accustomed to the arrangement that they began calling out for more. At that moment, when the expectation of harmlessness had been not merely conditioned but actively rewarded, Allied soldiers threw a live grenade.

It must be stated at the outset that this anecdote resists precise historical verification. Trench memoirs and unit diaries from 1914-1918 are voluminous but uneven. Whether it happened exactly as described, or at all, is less important than what its structure reveals about the ruse-perfidy boundary, which was contested in 1914, codified in 1977, and remains operationally live today.

The Law in 1914-1918

The applicable framework in 1914-1918 was reflected in the Hague Regulations of 1907, specifically the Regulations Respecting the Laws and Customs of War on Land annexed to Hague Convention IV, supplemented by the customary law of war that had crystallized in the preceding decades, including through the Brussels Declaration of 1874 and the Oxford Manual of 1880.

Article 23(b) of the Hague Regulations prohibited “treacherous killing or wounding” of enemy combatants. The term “treacherous” (perfide in the authoritative French text) carried the meaning that Vattel and earlier publicists had given it: killing by a method that abused the confidence of the adversary in a protected relationship, a flag of truce, a signal of surrender, a claim of medical status. It did not, on its face or in its doctrinal history, extend to the exploitation of ordinary tactical expectations. Article 24 of the same instrument explicitly preserved “stratagems” and “the employment of measures necessary for obtaining information about the enemy” as lawful. The Brussels Declaration had similarly distinguished between “forbidden treachery” and “permitted stratagems.”

The customary understanding was reinforced by military manuals of the period. Chapter XIV of the British Manual of Military Law (1914 edition) treated ruses as presumptively lawful, reserving the prohibition for acts involving “abuse of the white flag or of the uniform of the enemy.” The Hague framework’s silence on the specific scenario is therefore itself informative: the drafters of 1907, building on decades of codification effort, had a reasonably well-developed conception of treachery, and it did not reach this far.

The Modern Framework

The modern codification is Article 37(1) of Additional Protocol I (AP I) (1977), which defines perfidy as acts “inviting the confidence of an adversary to lead him to believe that he is entitled to, or is obliged to accord, protection under the rules of international law applicable in armed conflict, with intent to betray that confidence.” The provision lists paradigmatic examples: feigning surrender; feigning incapacitation due to wounds; feigning civilian status; and feigning protected status under the UN emblem or the Red Cross.

Article 37(2), by contrast, explicitly preserves ruses of war as lawful, defining them as acts “intended to mislead an adversary or to induce him to act recklessly but which do not infringe any rule of international law applicable in armed conflict and which do not invite the confidence of an adversary in protections.” The provision enumerates examples: camouflage; decoys; mock operations; and misinformation.

The critical structural distinction is therefore not deception as such, but the source of the confidence being exploited. Perfidy exploits confidence derived from the legal protections of international humanitarian law (IHL). Ruses exploit confidence derived from ordinary tactical or sensory expectations. This is the same distinction that the Hague framework embodied, now stated with greater precision.

In the first phase of the anecdote, the systematic throwing of ration tins, there is no legal difficulty under either the 1907 or the 1977 framework. Deceiving the enemy into believing an inert object is a grenade is a quintessential ruse. It exploits the adversary’s auditory expectations and conditioned reflexes. This is camouflage in acoustic form.

The second phase, throwing the live grenade once the expectation of harmlessness has been established, is where the analysis becomes genuinely contested. One position, grounded in Article 37 and supported by the Hague Regulations’ conception of treachery, holds that the tactic remains lawful throughout. The confidence exploited when the live grenade is thrown is not grounded in any IHL norm; it is grounded in prior tactical experience.

A second position argues that by the time the live grenade is thrown, the Allies have affirmatively cultivated an expectation of non-harm so systematically that the tactic begins to approximate, in functional terms, the trust-betrayal that perfidy prohibits. The German soldiers calling out for more tins have been operationally conditioned to understand the object as harmless.

Contemporary Relevance

In the cyber domain, the scenario maps directly onto a tactic that has been theorized and, in various forms, reportedly employed. A party conducts repeated network intrusions that appear benign, low-level probes causing no damage, generating alerts that operators learn to discount, before launching a destructive payload through the same vector. But by the time the destructive operation executes, a systematic expectation of harmlessness has been deliberately cultivated. The Tallinn Manual 2.0 addresses perfidy in cyber operations by applying Article 37’s framework directly, concluding that cyber perfidy requires the exploitation of IHL-based protections (Section 8).

If an autonomous system is programmed to identify certain behavioral signatures as non-threatening, and an adversary deliberately trains its own forces to exhibit those signatures before transitioning to hostile action, the “conditioning” at issue is embedded in algorithmic pattern recognition rather than human psychology. The legal question is formally the same: is exploiting a machine-learned expectation of harmlessness a ruse or something more? The answer under current doctrine is almost certainly “ruse.” Still, the policy implications are considerable, particularly as the speed and scale of autonomous systems make behavioral conditioning a more systematically deployable tool than it was in the trenches of Flanders.

Finally, the anecdote speaks to the use of feint and deception in contemporary hybrid operations. Forces that repeatedly conduct activities at the threshold of armed conflict and then exploit the adversary’s habituation to those activities to mask a genuine offensive operation, are doing what the Allied soldiers allegedly did with the tins. The law permits this. Whether the law should permit this, and whether the ruse-perfidy distinction as currently drawn is adequate to the operational environments of the twenty-first century, is a question that the tin can anecdote poses with remarkable clarity.

Conclusion

Assessed against the law as it stood in 1914-1918, the tin can tactic was lawful. Assessed against the modern framework of Article 37 AP I, it remains so. The confidence exploited was tactical, not legal. Under the positive law as it stands, that places the tactic firmly on the ruse side of the line. The Hague Regulations’ prohibition on treacherous killing and AP I’s definition of perfidy share a common structural commitment: the line is drawn at the abuse of IHL protections. The anecdote sits on the lawful side of that line.

But it sits very close to it: close enough that the same question, transposed into cyber operations and autonomous systems, poses one of the most practically consequential issues in the contemporary law of armed conflict. The soldiers of the Western Front, tossing ration tins into the dark, were conducting a legal experiment whose results we are still tabulating.

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Davit Khachatryan is an international law expert and researcher with a focus on operational law, international criminal law, alternative dispute resolution, and the intersection of various legal disciplines.

The views expressed are those of the author, and do not necessarily reflect the official position of the United States Military Academy, Department of the Army, or Department of Defense.

Articles of War is a forum for professionals to share opinions and cultivate ideas. Articles of War does not screen articles to fit a particular editorial agenda, nor endorse or advocate material that is published. Authorship does not indicate affiliation with Articles of War, the Lieber Institute, or the United States Military Academy West Point.

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