- Building defensive earthworks
- Cutting down fruit trees and burning crops unnecessarily
- Destroying only enemy armories
- Fortifying cities with trenches
The correct answer is “Cutting down fruit trees and burning crops unnecessarily.” This prohibition, famously instructed by Caliph Abu Bakr to his commander Usama ibn Zayd, is a remarkable early example of environmental protection during war. The rule is based on the principle of avoiding wanton destruction (ifsād) that does not serve a clear, necessary military objective. Destroying means of sustenance like fruit trees and crops primarily harms the civilian population long after the conflict ends, leading to famine and ecological damage. However, if such destruction is a military necessity—for example, to deprive a besieged enemy fortress of food—it may be permitted. The key is necessity and proportionality. This rule highlights the advanced ethical considerations in Islamic law regarding the protection of the environment and civilian livelihood.
