Related Rule
Netherlands
Practice Relating to Rule 20. Advance Warning
The Military Manual (1993) of the Netherlands states: “Whenever circumstances permit, advance warning must be given of an attack which may affect the civilian population.” 
Netherlands, Toepassing Humanitair Oorlogsrecht, Voorschift No. 27-412/1, Koninklijke Landmacht, Ministerie van Defensie, 1993, p. V-12.
The Aide-Mémoire for IFOR Commanders (1995) of the Netherlands states:
A warning must be given before opening fire if operational circumstances permit. A few examples of situations in which it is permitted to open fire without warning are:
a. if you or someone in your immediate vicinity are the subject of an armed attack; or
b. if warning enhances the risk of death or serious injury for you or any other person. 
Netherlands, Aide-Mémoire voor IFOR Commandanten, First Edition, 21 December 1995, § 5.
The Military Manual (2005) of the Netherlands states: “Effective warning should be given before any delivery of mines, booby-traps and other mechanisms which might affect the civilian population, unless circumstances do not permit this.” 
Netherlands, Humanitair Oorlogsrecht: Handleiding, Voorschift No. 27-412, Koninklijke Landmacht, Militair Juridische Dienst, 2005, § 0447.
In its chapter on behaviour in battle, the manual states: “In the case of an attack on cultural property as defined above [in situations of imperative military necessity], it must be possible in some way to give suitable advance warning.” 
Netherlands, Humanitair Oorlogsrecht: Handleiding, Voorschift No. 27-412, Koninklijke Landmacht, Militair Juridische Dienst, 2005, § 0528.
With regard to precautions in attack, the manual states: “Thought must be given to … whether or not to warn the civilian population.” 
Netherlands, Humanitair Oorlogsrecht: Handleiding, Voorschift No. 27-412, Koninklijke Landmacht, Militair Juridische Dienst, 2005, § 0542; see also § 0826 (protection of the civilian population).
The manual further provides:
If circumstances permit, advance warning should be given of an attack which may also affect the civilian population, to allow the authorities the opportunity to evacuate the civilian population. It is not obligatory to warn the civilian population of an attack where surprise is a decisive factor. 
Netherlands, Humanitair Oorlogsrecht: Handleiding, Voorschift No. 27-412, Koninklijke Landmacht, Militair Juridische Dienst, 2005, § 0545.
In its chapter on non-international armed conflict, the manual states: “If circumstances permit, a warning should be given before an attack that might also affect the civilian population.” 
Netherlands, Humanitair Oorlogsrecht: Handleiding, Voorschift No. 27-412, Koninklijke Landmacht, Militair Juridische Dienst, 2005, § 1044.
According to the Government of the Netherlands, commanders have to take all the precautionary measures required by Article 57 of the 1977 Additional Protocol I when carrying out an attack. 
Netherlands, Lower House of Parliament, Memorandum in response to the report on the ratification of the Additional Protocols, 1985–1986 Session, Doc. 18 277 (R 1247), No. 6, 16 December 1985, p. 7, § 17.