क्षत्रिय kṣatriya

The kṣatriya is the warrior, the ruler, the protector. The four varṇas of classical Indian social theory are brahmin (priest, scholar), kṣatriya (warrior, ruler), vaiśya (producer, trader), and śūdra (servant). The Mahābhārata’s principal cast is overwhelmingly kṣatriya; the war is between two branches of the same kṣatriya family; the questions of dharma the epic agonizes over are most often kṣātra-dharma, the duties specific to that station.

What the epic insists on, repeatedly, is the cost of kṣātra-dharma. To be a kṣatriya is to be willing to use force; to be unwilling to use force is to fail at the most basic obligation of the role. Yudhiṣṭhira keeps trying to refuse, and the text keeps showing him that refusal is not available without consequence.