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Spain
Practice Relating to Rule 15. The Principle of Precautions in Attack
Section C. Feasibility of precautions in attack
Spain’s LOAC Manual (2007) states:
Those responsible for planning and deciding on attacks must take “all feasible precautions” in the choice of means and methods of attack, with a view to “minimizing” the number of casualties among the civilian population, and “do everything feasible” to verify that the military objectives to be attacked are not protected persons or property. 
Spain, Orientaciones. El Derecho de los Conflictos Armados, Tomo 1, Publicación OR7–004, (Edición Segunda), Mando de Adiestramiento y Doctrina, Dirección de Doctrina, Orgánica y Materiales, 2 November 2007, § 2.4.c.(6).
Upon ratification of the 1977 Additional Protocol I, Spain interpreted the term “feasible” as meaning that “the matter in question is feasible or possible in practice, taking into account all the circumstances prevailing at the time, including humanitarian and military aspects”. 
Spain, Interpretative declarations made upon ratification of the 1977 Additional Protocol I, 21 April 1989, § 3.