Yuyudhana (Sanskrit: युयुधान, Yuyudhāna), better known as Satyaki (Sanskrit: सात्यकी, Sātyakī), was a powerful warrior belonging to the Vrishni clan of the Yadavas, to which Krishna also belonged. According to the Puranas, he was grandson of Shini of the Vrishni clan, and son of Satyaka. Satyaki was devoted to Krishna and was student of Arjuna as well as co-student under Dronacharya. Satyaki was a valiant warrior and on one particular occasion, Drona was stunned when Satyaki broke his bow for 101 times successively. He is also known as the unconquerable Satyaki.
Kurukshetra War 
Satyaki strongly and passionately favored the cause of the Pandavas over the Kauravas in the Kurukshetra War. Satyaki accompanied Krishna to the Kuru capital, with Krishna as the emissary of peace which was ridiculed and turned down by Duryodhana.
In the course of the fourteenth day of the conflict, Satyaki fights an intense battle with archrival Bhurisravas with whom he has a long standing family feud. After a long and bloody battle, Satyaki begins to tire, and Bhurisravas batters him and drags him across the battlefield. Arjuna is warned by Lord Krishna of what is happening. Bhurisravas prepares to kill Satyaki, but he is rescued from death by Arjuna, who shoots an arrow cutting off Bhurisravas' arm. Bhurisrava wails out that by striking him without warning, Arjuna had disgraced the honor between warriors. Arjuna rebukes him for attacking a defenseless Satyaki. He reiterates that protecting Satyaki's life at all costs was his responsibility as a friend and comrade in arms. Satyaki then emerges from his swoon, and swiftly decapitates his enemy. He is condemned for this rash act, but every soldier present realizes that the power of Krishna made Satyaki end Bhurisravas' life, which was going to happen anyway.
Yadava Warrior 
In the Kurukshetra war, Satyaki and Kritavarma were two important Yadava heroes who fought on the opposing sides. Satyaki fought on the side of the Pandavas, whereas Kritavarma joined the Kauravas. a fight between satyaki and satyajit is described in dron parva of mahabharat.
Satyaki and Kritavarma both survived the Kurukshetra conflict. Kritavarma is involved in the slaughter of the Panchalas and the sons of the Pandavas in the undeclared night attack with Kripacharya and Ashwatthama. 36 years after the war, the Yadavas, including Satyaki and Kritavarma are involved in a drunken brawl with Satyaki accusing Kritavarma of killing sleeping soldiers and Kritavarma criticizing Satyaki for his beheading of the unarmed Bhurisravas. In the ensuing melee, Satyaki, Kritavarma and the rest of the Yadavas are exterminated, as it was ordained by Gandhari's curse. Krishna desired to remove the Yadava clan from earth at the same time as his Avatar is fulfilled, so that the earth may be free of any possibly sinful and aggressive warriors, which was the wider purpose of the Kurukshetra war.
Satyaki is also noted as an ayurvedic physician who was an expert in Shalya (surgery) and Shalakya (Eye and E.N.T.), he is mentioned by Dalhana in Timir and Annantvat(sushrut Uttartantra) and by Chakrapani in Netraroga (Charak).
See also 
- Pargiter, F.E. (1972) . Ancient Indian Historical Tradition, Delhi: Motilal Banarsidass, p.107.
- Pargiter, F.E. (1972) . Ancient Indian Historical Tradition, Delhi: Motilal Banarsidass, p.284.