The fact that “Dharma” is an extremely subjective issue is well known. In any given situation, the answer to “What is the right thing to say/do?” is tricky to determine. Having the right principles and firm belief in those principles is what comes handy in situations requiring a finer interpretation of Dharma.
In the Mahabharata, Lord Bhimasena is a follower of the Bhagavata Dharma. One of the principles of this route is complete surrender to the Supreme Lord Vishnu. For the followers of this path, whatever Lord Vishnu states constitutes Dharma. Bhimasena demonstrates this on numerous occasions. One such occasion was the slaying of Dronacharya.
On the 15th day of the great war, when Acharya Drona was staging an impressive battle destroying thousands of Pandavas, Lord Krishna decides that the time to end Drona has come. He instructs the Pandavas to adopt a seemingly incorrect method to kill Drona. He advises them to tell Drona that Ashwathama has been slain. This, he says, will make Drona lay down his arms. The reaction of the Pandavas clearly reflects the extent to which they follow Dharma. I reproduce the below paragraph from Ganguly’s translation of the Mahabharata.
“Beholding the sons of Kunti afflicted with the shafts of Drona and inspired with fear, Kesava, endued with great intelligence and, devoted to their welfare, addressed Arjuna and said, ‘This foremost of all bowmen is incapable of being ever vanquished by force in battle, by the very gods with Vasava at their head. When, however, he lays aside his weapons, he becomes capable of being slain on the field even by human beings. Casting aside virtue, ye sons of Pandu, adopt now some contrivance for gaining the victory, so that Drona of the golden car may not slay us all in battle. Upon the full of (his son) Aswatthaman he will cease to fight, I think. Let sonic man, therefore, tell him that Aswatthaman, hath been slain in battle.’ This advice, however, O kin was not approved by Kunti’s son, Dhananjaya. Others approved of it. But Yudhishthira accepted it with great difficulty. Then the mighty-armed Bhima, O king, slew with a mace a foe-crushing, terrible and huge elephant named Aswatthaman, of his own army, belonging to Indravarman, the chief of the Malavas. Approaching Drona then in that battle with some bashfulness Bhimasena began to exclaim aloud, ‘Aswatthaman hath been slain.‘ That elephant named Aswatthaman having been thus slain, Bhima spoke of Aswatthaman’s slaughter…”
All the Pandavas know very well that Krishna is the Supreme Lord himself. Still, Arjuna outrightly rejects the advice. Arjuna’s action is even more difficult to comprehend because just 15 days earlier, he listens to the Gita and swears that he would completely follow Krishna’s instructions (Bhagavadgita – Chapter 18 – Shloka 73). Clearly, this constituted a complete deviation from Dharma. Yudhishtira only hesitatingly accepts to do this.
Bhimasena, on the other hand, proceeds to kill an elephant named Ashwathama and immediately informs Drona that Ashwathama has been killed. Drona, expectedly does not believe him because he knows that Bhimasena always does what Krishna asks him to do. So, he questions Yudhishthira. According to me, Bhimasena’s anticipates this and therefore kills the elephant. Otherwise, if Drona would accept his word itself, Bhimasena wouldn’t have even blinked to say the same without even bothering to kill the elephant.
Yudhisthira, with great difficulty, tells Drona that Ashwathama has died. He whispers at the end that it was an elephant that had died (“Ashwathamo hatha kunjaraha”). The chariot of Yudhisthira, which always stayed a few inches above the ground, comes down after this “Adharma”. Outwardly, it would appear that the chariot came down because of the lie. But, the real reason is that Yudhisthira did not follow the words of Krishna, which was Adharma and hence the chariot came down.
One of the names of Vishnu in the Vishnu Sahasranama is Dharma (“Dharmo dharmaviduttamaha….”). The Dharma in the world is governed by Krishna. What he says is Dharma. Hence, Yudhisthira not following Krishna’s words is very much against Dharma.
There is one more reason why Yudhishthira did a grave mistake. Just before the commencement of the war, on the battlefield, the Pandavas approach Bhishma and Drona. They seek their blessings and ask them how they can be slain. At that time, Drona clearly tells them (link – Page 101) that they would need to make him give up his arms in order to kill him. In effect, Drona permits them to do whatever is necessary to make him give up arms. So, Krishna was only advising them to follow the option provided by Drona. Even after this, Yudhisthira refuses to comply!