In the Mahabharata epic, which describes the Kurukshetra war, the two sides agree on the following rules:
Fighting must begin no earlier than sunrise and should end by exact sunset. (Broken on the 14th day, after Jayadratha was slain).
Multiple warriors must not attack a single warrior. (Broken several times, most notably in the 13th day, when Abhimanyu was slain).
Two warriors may duel, or engage in prolonged personal combat, only if they carry the same weapons and they are on the same mount (no mount, a horse, an elephant, or a chariot). (Broken several times).
No warrior may kill or injure a warrior who has surrendered. (Violated when Satyaki slew an unarmed Burishravas).
One who surrenders becomes a prisoner of war and will then be subject to the protections of a prisoner of war. (There were no prisoners of war taken, in the Kurukshetra War).
No warrior may kill or injure an unarmed warrior. (Arjuna slew Karna when the latter was helpless).
No warrior may kill or injure an unconscious warrior. (Broken when Abhimanyu was slain).
No warrior may kill or injure a person or animal not taking part in the war. (Broken several times when warriors slew horses of their enemies).
No warrior may kill or injure a warrior whose back is turned away. (Shakuni broke that rule).
No warrior may strike an animal not considered a direct threat.
The rules specific to each weapon must be followed. For example, it is prohibited to strike below the waist in mace warfare.
Warriors must not engage in any 'unfair' warfare whatsoever.
The lives of women, prisoners of war, and farmers are sacred.
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