In the Bhagavad Gita, the battlefield of “कुरुक्षेत्रे” (kuru-kṣhetre) is described as the “धर्मक्षेत्रे” (dharma-kṣhetre), or the sacred ground of supreme and timeless dharma. Krishna exhorts Arjuna to overlook the manmade tenets of morality, ethics and legality, and focus on fighting to win the great civilizational war. He reminds Arjuna that he is standing on religious ground and his primal duty is to wage war and annihilate the forces of evil that are threatening dharma and civilization.
The tenets of morality, ethics and legality, being manmade social constructs, are not superior to dharma and civilization. These tenets apply only in times of peace. When dharma and civilization are under threat, then the warriors and politicians must overlook morality, ethics and legality, and fight to destroy the enemy by every possible means.