The two sides summon vast armies to their help and line up at Kurukshetra for a war. The kingdoms of Panchala, Dwaraka, Kasi, Kekaya, Magadha, Matsya, Chedi, Pandyas, Telinga, and the Yadus of Mathura and some other clans like the Parama Kambojas were allied with the Pandavas. The allies of the Kauravas included the kings of Pragjyotisha, Anga, Kekaya, Sindhudesa (including Sindhus, Sauviras and Sivis), Mahishmati, Avanti in Madhyadesa, Madra, Gandhara, Bahlika people, Kambojas and many others. Before war being declared, Balarama had expressed his unhappiness at the developing conflict and leaves to go on pilgrimage; thus he does not take part in the battle itself. Krishna takes part in a non-combatant role, as charioteer (Sarathy) for Arjuna and offers Narayani Sena consisting of Abhira gopas to the Kauravas to fight on their side.[66][67]
Before the battle, Arjuna, noticing that the opposing army includes his cousins and relatives, including his grandfather Bhishma and his teacher Drona, has grave doubts about the fight. He falls into despair and refuses to fight. At this time, Krishna reminds him of his duty as a Kshatriya to fight for a righteous cause in the famous Bhagavad Gita section of the epic.
Though initially sticking to chivalrous notions of warfare, both sides soon adopt dishonorable tactics. At the end of the 18-day battle, only the Pandavas, Satyaki, Kripa, Ashwatthama, Kritavarma, Yuyutsu and Krishna survive. Yudhisthir becomes King of Hastinapur and Gandhari curses Krishna that the downfall of his clan is imminent.