§ 149. In former times invading armies frequently used to fire and destroy all enemy property they could not make use of or carry away. Afterwards, when the practice of warfare grew milder, belligerents in strict law retained the right to destroy enemy property according to discretion, although they did not, as a rule, any longer make use of such right. Nowadays, however, this right is obsolete. For in the nineteenth century it became a universally recognised rule of International Law that all useless and wanton destruction of enemy property, be it public or private, is absolutely prohibited. And this rule has now been expressly enacted by article 23 (_g_) of the Hague Regulations, where it is categorically enacted that "to destroy ... enemy's property, unless such destruction ... be imperatively demanded by the necessities of war, is prohibited." [Sidenote: Destruction for the purpose of Offence and Defence.] § 150. All destruction of and damage to enemy property for the purpose of offence and defence is _necessary_ destruction and damage, and therefore lawful. It is not only permissible to destroy and damage all kinds of enemy property on the battlefield during battle, but also in preparation for battle or siege. To strengthen a defensive position a house may be destroyed or damaged. To cover the retreat of an army a village on the battlefield may be fired. The district around an enemy fortress held by a belligerent may be razed, and, therefore, all private and public buildings, all vegetation may be destroyed, and all bridges blown up within a certain area. If a farm, a village, or even a town is not to be abandoned but prepared for defence, it may be necessary to damage in many ways or entirely destroy private and public property. Further, if and where a bombardment is lawful, all destruction of property involved in it becomes likewise lawful. When a belligerent force obtains possession of an enemy factory for ammunition or provisions for the enemy troops, if it is not certain that they can hold it against an attack, they may at least destroy the plant, if not the buildings. Or if a force occupies an enemy fortress, they may raze the fortifications. Even a force intrenching themselves on a battlefield may be obliged to resort to the destruction of many kinds of property. [Sidenote: Destruction in marching, reconnoitring, and conducting Transport.] § 151. Destruction of enemy property in marching troops, conducting military transport, and in reconnoitring, is likewise lawful if unavoidable. A reconnoitring party need not keep on the road if they can better serve their purpose by riding across the tilled fields. And troops may be marched and transport may be conducted over crops when necessary. A humane commander will not unnecessarily allow his troops and transport to march and ride over tilled fields and crops. But if the purpose of war necessitates it he is justified in so doing.