A great freedom of choice is given to belligerents in the selection of their instruments of warfare. Still not every instrument of destruction is permissible. The general restrictive principle is, that no instruments can be used which inflict unnecessary suffering, or which cause suffering all out of proportion to the benefit which it gives to the party using it. Poison in any form and explosive bullets are among the prohibited instruments. The use of uncivilized troops is also prohibited. The use of balloons, torpedoes, and mines are permissible.

11Wilson and Tucker on International Law, Sec. 100.

12 Id.