The story of Drona's birth is recounted dramatically in Mahābhārata, Book I: Adi Parva, Sambhava Parva, Section CXXXI. Bharadwaja went with his companions to the Ganges to perform his ablutions. There he beheld a beautiful apsara named Ghritachi who had come to bathe. The sage was overcome by desire, causing him to ejaculate. Bharadwaja captured the fluid in a vessel called a drona, and Drona himself sprang from the fluid thus preserved. Drona would later boast that he had sprung from Bharadwaja without ever having been in a womb.
Drona spent his youth in poverty, but studied religion and military arts together with the then prince of Panchala, Drupada. Drupada and Drona became close friends and Drupada, in his childish playfullness, promised to give Drona half his kingdom upon ascending the throne of Panchala.
Drupada gives Drona a long and haughty explanation of why he is rejecting him. Friendship, says Drupada, is possible only between persons of equal station in life. As a child, he says, it was possible for him to be friends with Drona, because at that time they were equals. But now Drupada had become a king, while Drona remained a luckless indigent. Under these circumstances, friendship was impossible. However, he said he would satisfy Drona if he begged for alms befitting a Brahmin rather than claiming his right as a friend. Drupada advised Drona to think no more of the matter, and to be on his way. Drona went away silently, but in his heart he vowed revenge Mahābhārata, Book I: Adi Parva, Sambhava Parva, Section CXXXII.
Drona laughed, and mildly rebuked the princes for being helpless over such a plain problem. Yudhisthira replied that if he, the brahmin, could retrieve their ball, the king of Hastinapura would provide all the basic necessities to him for life. Drona first threw in a ring of his, collected some grass blades, and uttered mystical Vedic chants. He then threw the blades into the well one after another, like spears. The first blade stuck to the ball, and the second stuck to the first, and so on, forming a chain. Drona gently pulled the ball out with this rope of grass.
In a feat that was even more amazing to the boys, Drona then chanted Vedic mantras again and fired a grass blade into the well. It struck within the center of his floating ring and rose out of the well in a matter of moments, retrieving Drona's ring. Excited, the boys took Drona to the city and reported this incident to Bhishma, their grandfather.
Bhishma instantly realized that this was Drona, and his prowess exemplified, asked him to become the Guru of the Kuru princes, training them in advanced military arts. Drona then established a school near the city, where princes from numerous kingdoms around the country came to study under him.
Mahābhārata, Book I: Adi Parva, Sambhava Parva, Section CXXXV Arjuna surpasses Drona's expectations in numerous challenges. When Drona tests the princes' alertness and ability by creating an illusion of a crocodile attacking him and dragging him away, most of the princes are left dumbfounded. But Arjuna swiftly fires arrows that slay the illusionary animal, and Drona congratulates Arjuna for passing this test. As a reward, Drona gives Arjuna the super-powerful divine weapon of Brahma known as Brahmastra,but tells Arjuna not to use this irresistible weapon against any ordinary warrior. The weapon had a sharp edge surrounded below by 3 heads of Lord Brahma. In another challenge, Drona gives each prince a pot to fill with water and swiftly return. Whoever returns fastest would receive instruction in some extra special knowledge. He gives his son Ashwathama a wide-necked pot unlike the other's narrow-necked ones, hoping he will be the first to return. But Arjuna uses his knowledge of a mystical water weapon to fill his pot swiftly and returns first.
Mahābhārata, Book I: Adi Parva, Sambhava Parva, Section CXXXIV - Section CXXXV) In a great challenge, Drona sets up a wooden bird upon a tree, and from across the adjacent river, asks the princes to shoot it down by striking its eye. When prince Yudhisthira tries first, Drona asks him what he saw. Yudhisthira replies he saw Drona, his brothers, the river, the forest, the tree and the bird. Drona replies that Yudhisthira would fail and asks another prince to step forward. The others give the same reply, and Drona is disappointed with all. But when Arjuna steps forth, he tells Drona that he sees only the eye of the bird and nothing else. When Drona excitedly asks him to continue, Arjuna replies that he saw only the bird's eye. Drona asks him to shoot, and Arjuna strikes the bird down in the eye.
One day Arjuna observed that his brother Bhima was eating in the night in complete darkness. He subtely observed that he was able to eat food in dark. By practice, hands would reach one's mouth even in darkness. This striked Arjuna to practice archery in darkness. He begins training by night to use his weapons in absolute darkness, and steadily achieves a great level of skill.
Drona is greatly impressed by Arjuna's concentration, determination and drive, and promises him that he will become the most powerful warrior on earth. Drona gives Arjuna special knowledge of the devastras that no other prince possesses.
Arjuna is worried that his position as the best warrior in the world might by usurped. Drona sees his worry, and visits Ekalavya with the princes. Ekalavya promptly worships Drona. Drona is angered by Ekalavya's unscrupulous behavior, claiming to be Drona's student despite his rejection. He is also worried that if Ekalavya maintained this level of skill, he would one day become warrior par-excellence than himself. The more important and personal reason seems to have been his partiality towards Arjuna. Drona asks Ekalavya for a dakshina, or a deed of thanks a student must give to his teacher upon the completion of his training. Drona asks for Ekalavya's right thumb, which Ekalavya unhesitatingly cuts off and hands to Drona, despite knowing that this would irreparably hamper his archery skills.
Drona similarly rejects Karna, as he does not belong to the kshatriya caste. Humiliated, Karna vows to exact revenge. He obtains the knowledge of weapons and military arts from Parasurama, by appearing as a brahmin, and challenges Arjuna in the martial exhibition. Thus, Drona inadvertently laid the foundation for Karna's great rivalry with Arjuna.
Drona is one of the most powerful and destructive warriors in the Kurukshetra War. He is an invincible warrior, whom no person on earth can defeat. He single-handedly slays hundreds of thousands of Pandava soldiers with his powerful armory of weapons and incredible skill. After the fall of Bhishma, he becomes the Chief Commander of the Kuru Army.
Drona had been the preceptor of most kings involved in the war, on both sides.
On the 13th day of battle, the Kauravas challenge the Pandavas to break a wheel shaped battle formation known as the Chakra Vyuha (see Wars of Hindu Mythology). Drona as commander forms this strategy as he knows that only Arjuna and Krishna know how to penetrate it. He asks the king of the Samshaptaka army to distract Arjuna and Krishna into another part of the battlefield, allowing the main Kuru army to surge through the Pandava ranks.
Arjuna's young son Abhimanyu is able to penetrate the formation, however, he is trapped when Jayadratha, the king of Sindhu holds the Pandava warriors following him at bay. Abhimanyu does not know how to get out of the Chakra Vyuha, but goes upon an all-out attack on the Kuru army, killing tens of thousands of warriors single-handedly. He even holds Karna and Drona himself at bay. Amazed at his prowess and courage, he is likened by the Kurus as his father's equal in greatness.
With his army facing decimation, Drona asks Karna, Dushasana and others to simultaneously attack Abhimanyu, to strike down his horses, his charioteer and to disable his chariot from different angles. Left without support, Abhimanyu begins fighting from the ground, whereupon all the Kuru warriors simultaneously attack him. Exhausted after his long, prodigious feats, Abhimanyu is weakened, grabs one of the wheels of his chariot and blocks all the attacks, but eventually he is killed by the simultaneous stabbing of seven swords.
All this was an extreme violation of the rules of war, whereby a lone warrior may not be attacked by more than one, and not at all if he is disabled or without chariot. This devious murder of his son enrages Arjuna, who swears to kill Jayadratha, whom he sees as responsible for his son's death. If he failed to do so the next day, he would step into fire and commit suicide.
Drona lines up the entire Kuru army, with millions of its soldiers in front of Arjuna to thwart his mission. But Arjuna exhibits his full prowess, and by the end of the day has killed more than a million warriors single-handedly. With the help of Krishna, he slays Jayadratha in the nick of time. But on the whole, Arjuna devastates the entire Kuru army dramatically in just one day of fighting.
On the 15th day of the Mahābhārata war, Drona, instigated by King Duryodhana's remarks of being a traitor, uses the BRAHMADANDA. This spiritual divine weapon contained the power of the 7 greatest sages of Hinduism. Drona had neither imparted the knowledge of this divine weapon to either Ashwattama or Arjuna. Thus, he proves unconquerable on the 15th day of war. Krishna asks Yudhisthira to proclaim that Drona's son Ashwathama has died, so that the invincible and destructive Kuru commander would give up his arms and thus could be killed. Bhima proceeds to kill an elephant named Ashwathama, and loudly proclaims that Ashwathama is dead.
Drona knows that only Yudhisthira, with his firm adherence to the truth, could tell him for sure if his son had died. When Drona approaches Yudhisthira to seek to confirm this, Yudhisthira tells him that Ashwathama is dead..., then, ..the elephant, but this last part is drowned out by the sound of trumpets and conchshells being sounded as if in triumph, on Krishna's instruction.
Yudhisthira cannot make himself tell a lie, despite the fact that if Drona continued to fight, the Pandavas and the cause of dharma itself would lose. When he speaks his half-lie, Yudhisthira's feet and chariot descend to the ground momentarily. Drona is disheartened, and lays down his weapons. He is then killed by Dhristadyumna.
It is said that Drona's soul, by meditation had already left his body before Dhristadyumna could strike. His death greatly saddens Arjuna, who had hoped to capture him alive.
Drona was no doubt partial towards Arjuna, in fact his love towards Arjuna was more than that towards his own son. Any great teacher would feel enthralled and satisfied only if his student excels and so was Drona. Drona was much parallel to Bhishma in thinking that he would fight for the cause of the kingdom, Hastinapura irrespective of who the ruler is.
Lord Krishna criticizes Drona for not speaking against or stopping the humiliation of Draupadi by Dushasana and Duryodhana. He is also criticized for being too proud and conceited, and for siding with evil despite the obvious righteousness of the Pandava cause.
It may also be concluded that he was responsible for the devious murder of Abhimanyu, as it was he who suggested simultaneously attacking and disabling the trapped Pandava hero. However, he remains a revered figure in Hindu mythology, and the basis for Indian traditions of respecting one's teacher as one would his or her parents.
It is believed that the city of Gurgaon (literal translation being "Village of the Guru") was founded by Drona; the land was awarded to him by Yudhisthir, the king of Hastinapur in recognition of his teachings of martial arts to the princes, and the 'Dronacharya Tank', still exists within the Gurgaon city, along with a village called Gurgaon.