Good faith, as expressed in the observance of promises, is essential in war, for without it hostilities could not be terminated with any degree of safety short of the total destruction of one of the contending parties.

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The borderline between legitimate ruses and forbidden treachery has varied at different times, and it is difficult to lay down hard and fast rules in the matter. Many of the doubtful cases, however, which arose at a time when, from the nature of their weapons, troops could only engage at close range, can now seldom or never occur. 

Perfidy is defined 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.” 

Acts inviting the confidence of an adversary to lead it to believe that it 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, constitute perfidy. 

The definition of perfidy in paragraph 5.9.1 [relating to international armed conflicts, quoted above] may also be used as guidance as to the meaning of “treachery” in internal armed conflicts. 

Assassination, the killing or wounding of a selected individual behind the line of battle by enemy agents or partisans, and the killing or wounding by treachery of individuals belonging to the opposing nation or army, are not lawful acts of war. The perpetrator of such an act has to claim to be treated as a combatant, but should be put on trial as a war criminal. If prior information of an intended assassination or other act of treachery should reach the government on whose behalf the act is to be committed, that government should endeavour to prevent its being carried out.

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It is not forbidden to send a detachment or individual members of the armed forces to kill, by sudden attack, members or a member of the enemy armed forces.

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In view of the prohibition of assassination, the proscription or outlawing or the putting of a price on the head of an enemy individual or any offer for an enemy “dead or alive” is forbidden.

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The prohibition extends to offers of rewards for the killing or wounding of all enemies, or of a class of enemy persons, e.g., officers … Offers of rewards for the capture unharmed of enemy personnel generally or of particular enemy personnel would seem to be lawful …

How far do the above rules apply to armed conflicts not of an international character occurring in the territory of a State, e.g., a civil war or large scale armed insurrection? The acts which are prohibited in such conflicts are those set out in common Art. 3 of the 1949 [Geneva] Conventions, see paras. 7 and 8. Para (1) (a) of that article forbids “murder of all kinds” in respect of persons who do not take an active part in the hostilities and those members of armed forces who have laid down their arms or who are hors de combat. If a government or military commander offers rewards for all or individual armed insurgents killed or wounded by the forces engaged in quelling the insurrection, such offers are open to the same objection as those set out above in respect of hostilities between belligerents and are probably unlawful. 

The Hague Regulations 1907 are now recognized as part of customary law. Those regulations provide that the following acts are “especially forbidden”:

It is forbidden to make improper use of a flag of truce. Thus, a feigned intention to negotiate or surrender with the intention of using the white flag as cover for the collection of information might amount to the war crime of perfidy whatever the consequences. It would amount to a grave breach of Additional Protocol I if it resulted in death or serious injury. A parlementaire who abuses his position in this way can be taken as a prisoner of war and tried. 

Coalition commanders have expressed considerable concern about the practice – which we have seen on more than one occasion – of Iraqi soldiers apparently surrendering but then attacking the forces to whom they appeared to be surrendering. That is clearly a serious breach of the Geneva convention and one that we will continue to highlight when appropriate. 

It is forbidden to make improper use of a flag of truce. Thus, a feigned intention to negotiate or surrender with the intention of using the white flag as cover for the collection of information might amount to the war crime of perfidy whatever the consequences. It would amount to a grave breach of Additional Protocol I if it resulted in death or serious injury. A parlementaire who abuses his position in this way can be taken as a prisoner of war and tried. 

Additional Protocol I extends the definition of grave breaches to include the following:

The parties to an armed conflict are prohibited to make use of the emblem of the United Nations except as authorized by the United Nations. In addition, it is prohibited to kill, injure or capture an adversary by feigning protected status by the use of signs, emblems or uniforms of the United Nations and to do so constitutes the war crime of perfidy. 

Additional Protocol I extends the definition of grave breaches to include the following:

Article 19 of the Hague Rules 1923 prohibited the use of false external marks on aircraft. Additional Protocol I now prohibits the use at any time by any party to a conflict of the flags, military emblems, insignia or uniforms of neutral or other states not party to the conflict. The use of flags, military emblems, insignia or uniforms of an adverse party is prohibited “while engaging in attacks or in order to shield, favour or impede military operations”.