Why does the Hague Convention of 1907 say that the right to injure an enemy is not unlimited?

Article 22 of the Regulations Annexed to the Hague Convention of 1907 states that the right of belligerents to adopt means of injuring the enemy is not unlimited.1

This principle is rooted in the ethical understanding that the only legitimate objective for states during war is to weaken the military forces of the enemy. Consequently, international law prohibits methods and means of warfare that cause unnecessary suffering or are treacherous in nature.1

Specifically, the convention and its associated regulations prohibit:
* The employment of poison or poisoned weapons.1
* Killing or injuring enemy combatants treacherously.1
* Attacking those who have surrendered.1
* Declaring that no quarter will be given.1
* The use of arms, projectiles, or materials calculated to cause unnecessary suffering.1

By establishing these limits, the Hague Convention seeks to uphold fundamental principles of humanity and protect individuals from excessive or cruel harm during armed conflict.12