In Sanskrit, the word Bhishma (?????) means 'one who undertakes a terrible vow(bheeshana Pratijna) and fulfills it.'

His other names are as follows-

• Devavrata (???????) -
• Gangaputra (?????????) - son of Ganga (Purity)
• Shantanava (???????) - descendant (son) of Shantanu
• Pitamaha (??????) - paternal grandfather
• Mahamahima (???????) - great king or the one who is excessively great
• Gauranga (??????) - the one with fair body
• Shvetaveera (????????) - a white warrior or the one who is heroic white
• Asta Vasu - elemental gods (in previous life)

The history behind Bhishma's birth is as follows — once the eight Vasus ("Ashtavasus") visited Vashishta's ashram accompanied by their wives. One of the wives took a fancy to Kamadhenu, Vashishta's wish-bearing cow and asked her husband Prabhasa to steal it from Vashishta. Prabhasa then stole the cow with the help of the others who were all consequently cursed by Vashishta to be born in the world of humans.

Upon the Vasus appealing to Vashishta's mercy, the seven Vasus who had assisted in stealing Kamadhenu had their curse mitigated such that they would be liberated from their human birth as soon as they were born; however, Prabhasa being protagonist of the theft, was cursed to endure a longer life on the earth. The curse, however is softened to the extent that he would be one of the most illustrious men of his time. It was this Prabhasa who took birth as Bhishma.

After Devavrata was born, his mother Ganga took him to different realms, where he was brought up and trained by many eminent sages (Mahabharata Shanti Parva, section 38).

• Brihaspati: The son of Angiras and the preceptor of the Devas taught Devavrata the duties of kings (Dandaneeti), or political science and other Shastras.
• Shukracharya: The son of Bhrigu and the preceptor of the Asuras also taught Devavrata in political science and other branches of knowledge.
• Vashishtha, the Brahmarshi and Chyavana, the son of Bhrigu taught the Vedangas and other holy scriptures to Devavrata who mastered the Vedas.
• Sanatkumara: The eldest son of Lord Brahma, taught Devavrata the mental and spiritual sciences, also called the Ânvîkshîkî.
• Markandeya: The immortal son of Mrikandu of Bhrigu's race who acquired everlasting youth from Lord Shiva taught Devavrata in the duties of Brahmanas.
• Parashurama: The son of Jamadagni of Bhrigu's race. Parashurama trained Bhishma in warfare.

Bhishma means He of the terrible oath, referring to his vow of lifelong Brahmacharya.Originally named Devavratha, he became known as Bhishma after he took the bhishamna pratignya ('terrible oath') — the vow of lifelong Brahmacharya and of service to whomever sat on the throne of his father (the throne of Hastinapur). He took this oath so that his father, Shantanu could marry a fisherwoman Satyavati — Satyavati's father had refused to give his daughter's hand to Shantanu on the grounds that his daughter's children would never be rulers. This made Shantanu despondent, and upon discovering the reason for his father's despondency, Devavratha sought out the girl's father and promised him that he would never stake a claim to the throne, implying that the child born to Shantanu and Satyavati would become the ruler after Shantanu. At this, Satyavati's father retorted that even if Devavratha gave up his claim to the throne, his (Devavratha's) children would still claim the throne. Devavratha then took the vow of lifelong celibacy, thus sacrificing his 'crown-prince' title and denying himself the pleasures of conjugal love. This gave him immediate recognition among the gods. His father granted him the boon of Ichcha Mrityu (control over his own death — he could choose the time of his death, making him immortal till his chosen time of death, instead of completely immortal which would have been an even more severe curse and cause of suffering).

Criticism of King Shantanu from his subjects as to why he removed Bhishma from the title of the crown prince, as he was so capable, abounded. There was worry about the nobility of Shantanu's unborn children, now promised the throne. Hearing this, Bhishma said it was his decision and his father should not be blamed as Shantanu had never promised anything to Satyavati's father. The prime minister then asked who would be held responsible if the future crown prince isn't capable enough. Bhishma then took another vow that he would always see his father's image in whomever sat on the King's throne, and would thus serve him faithfully.

Years later, in the process of finding a bride for his half-brother, the young king Vichitravirya, Bhishma abducted princesses Amba, Ambika and Ambalika of Kashi (Varanasi) from the assemblage of suitors at their swayamvara. Salwa, the ruler of Saubala, and Amba (the eldest princess) were in love; Salwa attempted to stop the abduction but was soundly beaten. Upon reaching Hastinapura, Amba confided in Bhishma that she wished to wed Salwa. Bhishma then sent her back to Salwa, who, bitter from his humiliating defeat at Bhishma's hands, turned her down. Disgraced, Amba approached Bhishma for marriage. He refused her, citing his oath. Enraged beyond measure, Amba vowed to avenge herself against Bhishma even if it meant being reborn over and over again.

Amba sought refuge with Parasurama, who ordered Bhishma to marry Amba, telling Bhishma it was his duty. Bhishma politely refused saying that he was ready to give up his life at the command of his teacher but not the promise that he had made. Upon the refusal, Parasurama called him for a fight at Kurukshetra. At the battlegrounds, while Bhishma was on a chariot, Parasurama was on foot. Bhishma requested Parasurama to also take a chariot and armor so that Bhishma would not have an unfair advantage. Parasurama blessed Bhishma with the power of divine vision and asked him to look again. When Bhishma looked at his guru with the divine eyesight, he saw the Earth as Parasurama's chariot, the four Vedas as the horses, the Upanishads as the reins, Vayu (wind) as the Charioteer and the Vedic goddesses Gayatri, Savitri, and Saraswati as his armor. Bhishma got down from the chariot and sought the blessings of Parashurama to protect his dharma, along with permission to battle against his teacher. Pleased, Parashurama blessed him and advised him to protect his vow as Parasurama himself had to fight to uphold his word as given to Amba. They fought for 23 days without conclusion, each too powerful to defeat the other.

In one version of the epic, on the 23rd day of battle, Bhishma attempted to use the Praswapastra against Parashurama.Learned in his previous birth as Prabhasa (one of Ashta Vasus), this weapon was not known to Parasurama and would put the afflicted to sleep in the battlefield. This would have given Bhishma the victory. Before he could release it, however, a voice from the sky warned him that "if he uses this weapon it would be a great insult towards his Guru." Pitrs then appeared and obstructed the chariot of Parashurama, forbidding him from fighting any longer. At the behest of the divine sage Narada and the gods, Parashurama ended the conflict and the battle was declared a draw by Gods.

Parashurama narrated the events to Amba and told her to seek Bhishma's protection. However, Amba refused to listen to Parashurama's advice and left angrily declaring that she would achieve her objective by asceticism. Her predicament unchanged, did severe penance to please Lord Shiva. Lord Shiva assured her that she would be born as a man named (Shikhandi) in her next birth (and still she would recall her past) and could be instrumental in Bhishma's death, thus satisfying her vow.^[6]

In the great battle at Kurukshetra, Bhishma was the supreme commander of the Kaurava forces for ten days. He fought reluctantly on the side of the Kauravas. Bhishma was one of the most powerful warriors of his time and in history. He acquired his prowess and invincibility from being the son of the sacred Ganga and by being a student of renowned Gurus. Despite being about five generations old, Bhishma was too powerful to be defeated by any warrior alive at that time. Every day, he slew at least 10,000 soldiers and about a 1,000 rathas. At the beginning of the war, Bhishma vowed not to kill any of the Pandavas, as he loved them, being their grand-uncle. Duryodhana often confronted Bhishma alleging that he was not actually fighting for the Kaurava camp as he wouldn't kill any of the pandavas. He also did not allow any of the Kauravas to be killed in the war, as he loved all his grand-nephews and wanted a peace negotiation.

Duryodhana approached Bhishma one night and accused him of not fighting the battle to his full strength because of his affection for the Pandavas. The angry Bhishma took a vow that either he will kill Arjuna or will make Lord Krishna break his promise of not picking up any weapons during the war. On the next day there was an intense battle between Bhishma and Arjuna. Although Arjuna was very powerful, he was no match for Bhishma. Bhishma soon shot arrows which cut Arjuna's armour and then also his Gandiva bow's string. Arjuna was helpless before the wrath of his grand-uncle. As Bhishma was about to kill Arjuna with his arrows, Sri Krishna who took vow of not raising a weapon in the war, lifted a chariot wheel and threatened Bhishma. Arjuna stopped Lord Krishna. Arjuna convinced Krishna to r