With the thirteen years fulfilled, the Pandavas claimed what the wager had promised: the return of their half of the kingdom. Duryodhana refused outright. Messages passed between the courts; tempers rose; both sides began to gather allies and armies. Yet even now, the war was not certain, and Yudhishthira, who loathed bloodshed, was willing to settle for far less than his due. So Krishna — friend, kinsman, and counsellor to the Pandavas, and the one figure both sides revered — agreed to go to Hastinapura himself as an ambassador of peace. This episode, the Udyoga Parva, the "book of effort," is the epic's last and most strenuous attempt to avert catastrophe.

Krishna's mission is framed as the exhaustion of every honourable alternative. Standing in the Kaurava assembly, he reduced the Pandavas' demand to almost nothing: not the kingdom, not a province, but five villages — one for each brother — and, in some tellings, he added that they would be content with even five houses. It was an offer pitched so low that to refuse it was to declare that the quarrel was no longer about land but about pride and the will to destroy. The elders — Bhishma, Drona, Vidura, even the blind Dhritarashtra — pleaded with Duryodhana to accept. He would not. His famous reply was that he would not yield territory enough to be balanced on the point of a needle without a war.

Then came the embassy's darkest turn. Duryodhana, against all the law that protects an envoy, plotted to seize and bind Krishna in open court. The attempt collapsed: Krishna revealed, for those with eyes to see, his Vishvarupa, the cosmic form blazing with all the gods and worlds, before which the hall trembled and the blind king begged for the sight to behold it. No chain could hold him. He left the court with the matter settled in the only way Duryodhana had left open.

Two private scenes deepen the tragedy. Krishna sought out Karna, the great Kaurava warrior, and revealed that he was secretly Kunti's firstborn — elder brother to the very Pandavas he was about to fight — offering him the throne itself if he would change sides. Karna, bound by loyalty and gratitude to Duryodhana who had befriended him when others scorned his birth, refused with sorrowful dignity. And on the eve of war, the rivals went to Krishna for aid: to one he gave his vast army, to the other he gave himself alone, unarmed, as charioteer. Arjuna chose Krishna. The embassy had failed, but its failure had drawn, with terrible clarity, the line between the side that begged for peace and the side that spurned it.