Bhagavad Gita · Arjuna Vishada YogaChapter 1, Shloka 12 (1.12)

"Tasya harṣaṃ sañjanayan" — to awaken his joy. The purpose of Bhishma's conch is clearly stated: to awaken joy in Duryodhana's heart. This in itself says a great deal. Joy needs to be awakened when there is gloom or fear in the mind. So many commentators (including Ramanuja's summary of the story) take this as support for the "anxious" reading of 1.10: seeing Duryodhana's despair, Bhishma gave him encouragement.

Madhusudana Sarasvati's deeper interpretation: Madhusudana offers a glimpse into Bhishma's mind. He says Bhishma saw how Drona treated Duryodhana — Drona did not answer him with even a word — and heard Duryodhana praising Bhishma. Then Bhishma, with the feeling "whether he praises me or blames me, this body will fall for him anyway", gave a lion-roar to cheer him. Three epithets support this interpretation:

• Kuru-vṛddha (eldest of the Kurus): so he understood what was in the minds of both Drona and Duryodhana.
• Pitāmaha (grandfather): so he could not ignore his grandson — he did not stay silent as Drona did.
• Pratāpavān (mighty): so that his lion-roar and conch would also strike fear into the enemy's mind.

Bhishma's tragic character: Bhishma's whole life is reflected in this single shloka. He is the commander of the Kaurava army, he loves the Pandavas, and he knows this war is on the side of injustice. Yet he is bound by his vow and by his duty to Hastinapura. His conch is a commander's duty — and also a grandfather's comfort to his wayward grandson.

The first conch — who blew it? In the Mahabharata story, the first conch of the war was blown from the Kaurava side, by the commander Bhishma. Sanjaya's account shows this same order.