Related Rule
Germany
Practice Relating to Rule 65. Perfidy
Section E. Simulation of an intention to negotiate under the white flag of truce
Under Germany’s Soldiers’ Manual (1991), “the feigning of the intention to negotiate under a flag of truce” constitutes a perfidious act. 
Germany, Taschenkarte, Humanitäres Völkerrecht in bewaffneten Konflikten – Grundsätze, Bearbeitet nach ZDv 15/2, Humanitäres Völkerrecht in bewaffneten Konflikten – Handbuch, Zentrum Innere Führung, June 1991, p. 2.
Germany’s Military Manual (1992) provides:
Misusing the flag of truce constitutes perfidy and hence a violation of international law … The flag of truce is being misused, for instance, if soldiers approach an enemy position under the protection of the flag of truce in order to attack. 
Germany, Humanitarian Law in Armed Conflicts – Manual, DSK VV207320067, edited by The Federal Ministry of Defence of the Federal Republic of Germany, VR II 3, August 1992, English translation of ZDv 15/2, Humanitäres Völkerrecht in bewaffneten KonfliktenHandbuch, August 1992, § 230; see also § 1019 (naval warfare).
The manual also states: “Grave breaches of international humanitarian law are in particular: … perfidious … use of recognized protective signs.” 
Germany, Humanitarian Law in Armed Conflicts – Manual, DSK VV207320067, edited by The Federal Ministry of Defence of the Federal Republic of Germany, VR II 3, August 1992, English translation of ZDv 15/2, Humanitäres Völkerrecht in bewaffneten KonfliktenHandbuch, August 1992, § 1209.
Germany’s Soldiers’ Manual (2006) states that perfidious acts are those “by which the adversary is induced to believe that there is a situation affording protection under public international law, so that he may be attacked by surprise, e.g. the feigning of … the intention to negotiate under the flag of truce.” 
Germany, Druckschrift Einsatz Nr. 03, Humanitäres Völkerrecht in bewaffneten Konflikten – Grundsätze, Erarbeitet nach ZDv 15/2, Humanitäres Völkerrecht in bewaffneten Konflikten – Handbuch, DSK SF009320187, Bundesministerium der Verteidigung, R II 3, August 2006, p. 2.
Germany’s Law Introducing the International Crimes Code (2002) punishes anyone who, in connection with an international or non-international armed conflict, “makes improper use … of the flag of truce, … thereby causing a person’s death or serious injury”. 
Germany, Law Introducing the International Crimes Code, 2002, Article 1, § 10(2).