Related Rule
Practice Relating to Rule 15. The Principle of Precautions in Attack
Section B. Avoidance or minimization of incidental damage
Germany’s Military Manual (1992) states: “When launching an attack on a military objective, all feasible precautions shall be taken to avoiding, and in any event to minimizing, incidental losses of civilian life, injury to civilians and damage to civilian objects.” 
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, § 510.
In 2010, in the Fuel Tankers case, the Federal Prosecutor General at Germany’s Federal Court of Justice investigated whether war crimes or other crimes under domestic law had been committed in the course of an airstrike which was ordered by a colonel (Oberst) of the German armed forces against two tankers transporting fuel for the International Security Assistance Force in Afghanistan stolen by the Taliban near Kunduz and which resulted in the deaths of a number of civilians. The Federal Prosecutor General stated:
Pursuant to § 170 para. 2 StPO [Penal Procedure Code], the investigation proceedings which were initiated by the order of 12 March 2010 against Colonel (Oberst) Klein and Company Sergeant Major (Hauptfeldwebel) Wilhelm due to suspected offences under the VStGB [International Crimes Code] and other offences are to be terminated as a result of the investigations conducted and based on the sources of information set out hereafter and on the reasons given in detail hereafter. 
Germany, Federal Court of Justice, Federal Prosecutor General, Fuel Tankers case, Decision, 16 April 2010, p. 1.
The Federal Prosecutor General also stated:
Criminal responsibility under § 211 StGB [i.e. for murder under Germany’s Penal Code]
Colonel (Oberst) Klein’s actions were lawful under international law and therefore justified under domestic criminal law …
Even considering the fact that the bombing killed civilians to be protected under the international law of armed conflict, the order to attack was lawful under international law.
… International humanitarian law … prohibits … attacks … against a military objective if at the time of the order to attack the anticipated civilian damage is out of proportion (“excessive” see Art. 51 para. 5 sub-para. b AP [1977 Additional Protocol] I) to the anticipated concrete and direct military advantage (see ICRC Customary International Humanitarian Law, 2005 – hereafter ICRC Customary IHL [Study] – p. 46ff). …
… Only if a commander refrained from taking feasible precautions in violation of international law (“feasible precaution”; see. Art. 57 para. 2 sub-para. a AP I; ICRC Customary IHL [Study] p. 51 ff.) and such precautions would have led to the anticipation of greater civilian collateral damage which then in fact materialized is thus relevant for an analysis of the proportionality of an attack. … In view of the circumstances known to Colonel (Oberst) Klein (distance to inhabited settlements, night time, presence of armed Taliban) and the informant’s statements, he considered the presence of protected civilians unlikely … Further feasible reconnaissance and precautionary measures (“feasible precautions”) were not promptly available in the concrete situation. 
Germany, Federal Court of Justice, Federal Prosecutor General, Fuel Tankers case, Decision, 16 April 2010, pp. 63–66.