Related Rule
United Kingdom of Great Britain and Northern Ireland
Practice Relating to Rule 156. Definition of War Crimes
The UK Military Manual (1958) states:
The term “war crime” is the technical expression for violations of the law of warfare, whether committed by members of the armed forces or by civilians. It has also been customary to describe as war crimes such acts as espionage and so-called war treason which, although not prohibited by international law, are properly liable to punishment by the belligerent against which they are directed. However, the accuracy of the description of such acts as war crimes is doubtful. 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 624.
The manual identifies a number of offences as war crimes, some of which are listed as grave breaches and some of which, under the heading “Other war crimes”, it describes as “examples of punishable violations of the laws of war, or war crimes”. 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, §§ 625 and 626.
Under the same heading, the manual adds: “Similarly, all other violations of the [1949 Geneva] Conventions not amounting to ‘grave breaches’ are also war crimes.” 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 626.
The UK LOAC Manual (2004) states:
Serious violations of the law of armed conflict, other than those listed as grave breaches in the [1949 Geneva] Conventions or [the 1977 Additional Protocol I], remain war crimes and punishable as such. A distinction must be drawn between crimes established by treaty or convention and crimes under customary international law. Treaty crimes only bind parties to the treaty in question, whereas customary international law is binding on all states. Many treaty crimes are merely codifications of customary law and to that extent binding on all states, even those that are not parties. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 16.26.
The manual further states:
16.39. A person is normally only guilty of a war crime if he commits it with intent and knowledge.
16.39.1. However, some war crimes contain an integral mental element. An example is the grave breach of wilful killing. This word can be interpreted as extending beyond intent and knowledge. The International Committee of the Red Cross explain wilfulness as follows:
wilfully: the accused must have acted consciously and with intent, i.e. with his mind on the act and its consequences and willing them …; this encompasses the concepts of ‘wrongful intent’ or ‘recklessness’, viz., the attitude of an agent who, without being certain of a particular result, accepts the possibility of it happening; on the other hand, ordinary negligence or lack of foresight is not covered, i.e., when a man acts without having his mind on the act or its consequences …”
In the decided cases, the issue of recklessness has not been relevant, as the offences were so obviously committed with intent, except in those cases where command responsibility is invoked where there is a different test.
16.39.2. The governing provisions for international tribunals and courts have not, in the past, sought to outline general principles of law but to concentrate on substantive matters. Thus it has been left to the tribunals and courts to develop their own jurisprudence on a case by case basis. The Statute of the International Criminal Court, for the first time, has sought to rectify this and provides, in Article 30, that “unless otherwise provided” the material element of an offence must be committed “with intent and knowledge”. Both “intent” and “knowledge” are separately defined. This text, however, implies that there are occasions when this test may be inappropriate and, indeed, in the elements of crimes there are provisions which depart from Article 30, introducing a “should have known” test.
16.39.3. National tribunals will normally be governed by the general principles of law contained in their own domestic legislation although these will undoubtedly be influenced by any international jurisprudence that may exist. The United Kingdom has adopted, for the purposes of offences under the International Criminal Court Act 2001, the definition of “intent” contained in the Rome Statute as well as the provisions on command/superior responsibility. On other issues, such as general defences, the ordinary criminal law will apply. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, §§ 16.39–16.39.3.
With regard to internal armed conflict, the manual states:
War Crimes
15.32. Although the treaties governing internal armed conflicts contain no grave breach provisions, customary law recognizes that serious violations of those treaties can amount to punishable war crimes.
15.32.1. It is now recognized that there is a growing area of conduct that is criminal in both international and internal armed conflict. This is reflected in Article 8 of the Rome Statute.
15.32.2. “Customary international law imposes criminal liability for serious violations of Common Article 3, as supplemented by other general principles and rules on the protection of victims of internal armed conflict, and for breaching certain fundamental principles and rules regarding means and methods of combat in civil strife.” 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, §§ 15.32–15.32.2.
The UK Regulations for the Trial of War Criminals (1945), as amended in 1946, states: “‘War crime’ means a violation of the laws and usages of war committed during any war in which His Majesty has been or may be engaged at any time since the 2nd September, 1939.” 
United Kingdom, Regulations for the Trial of War Criminals, 1945, as amended in 1946, Regulation 1.
The UK International Criminal Court Act (2001) (Elements of Crimes) (No. 2) Regulations 2004 (2004), a UK Statutory Instrument made pursuant to Section 50(3) of the 2001 UK International Criminal Court Act, sets out the text of the Elements of Crimes adopted by the Assembly of States Parties of the ICC on 9 September 2002 in accordance with Article 9(1) of the ICC Statute. 
United Kingdom, International Criminal Court Act 2001 (Elements of Crimes) (No. 2) Regulations 2004, 2004, Sections 1–3 and Schedule.
The purpose of the Statutory Instrument is to apply the Elements of Crimes in domestic law, to be taken into account by UK courts when interpreting and applying the provisions of the 2001 UK International Criminal Court Act.
In the Zyklon B case in 1946, the UK Military Court at Hamburg convicted Bruno Tesch and Karl Weinbacher, civilian entrepreneurs, for the commission of a war crime in that they “at Hamburg, Germany, between 1st January, 1941, and 31st March, 1945, in violation of the laws and usages of war did supply poison gas used for the extermination of allied nationals interned in concentration camps well knowing that the said gas was to be so used.” Bruno Tesch was owner of a firm which arranged for the supply of poison gas (Zyklon B) intended for the extermination of vermin. Karl Weinbacher was Tesch’s procurist or second-in-command. Joachim Drosihn was the firm’s fist gassing technician. The defence claimed that the accused did not know of the use to which the gas was to be put. For Drosihn it was also pleaded that the supply of gas was beyond his control. Tesch and Weinbacher were condemned to death. Drosihn was acquitted. 
United Kingdom, Military Court at Hamburg, Zyklon B case, Judgment, 1–8 March 1946.
In 2003, in a written reply to a question in the House of Commons, the UK Minister of State for Defence stated:
The offences contained in the Statute of the International Criminal Court (ICC) reflect international law provisions that were already applicable to the conduct of United Kingdom of Great Britain and Northern Ireland forces in any theatre of engagement. The ICC Statute does not therefore impose new conditions.
The consequences for our forces of UK ratification of the ICC Statute were carefully examined in preparation for the ICC Act 2001. Under the Statute, investigation and, if necessary prosecution of any allegations of war crimes, crimes against humanity or genocide by a UK national would be carried out by the UK. The Court would intervene only if it determined that a state was unwilling or unable to pursue a particular case, but it is inconceivable that the UK would ever be unable or unwilling to investigate or take appropriate action. 
United Kingdom, House of Commons, Written answer by the Minister of State for Defence, Hansard, 28 January 2003, Vol. 398, Written Answers, col. 836W.