As an unborn child in his mother's womb, Abhimanyu learns the knowledge of entering the deadly and virtually impenetrable Chakravyuha (see Wars of Hindu Mythology) from Arjuna.The epic explains that he overheard Arjuna talking about this with his mother from the womb. Arjuna spoke about entering Chakravyuha and later Subhadra dozed to sleep. Arjuna stopped explaining Chakravyuha escape when he saw Subhadra slept while listening. As an effect, the baby Abhimanyu in womb didn't get a chance to know of coming out of it.
Abhimanyu spent his childhood in Dwaraka, his mother's city. He was trained by Pradyumna, the son of Sri Krishna and his great warrior father Arjuna and brought up under the guidance of Lord Krishna. His father arranged his marriage to Uttara, daughter of king Virata to seal an alliance between the Pandavas and the royal family of Virata, in lieu of the forthcoming Kurukshetra War. The Pandavas had been hiding in cognito to live through the final year of their exile without being discovered, in Virata's kingdom of Matsya.
Being the grandson of Lord Indra, god of mystical weapons and wars responsible for killing thousands of enemy heroes and hundreds of thousands of warriors, Abhimanyu was a courageous and dashing warrior. Considered equal to his father's level owing his prodigious feats, Abhimanyu was able to hold at bay, great heroes like Drona, Karna, Duryodhana and Dushasana. He was praised for his audacious bravery and absolute loyalty to his father, his uncles and to their cause.
Abhimanyu has taken part in the war of Mahabharat and killed important personalities such as Kumara Lakshmana, the son of Duryodhana and Brihadbala, the king of Kosala belonging to Ikshwaku dynasty.
On the 13th day of battle, the Kauravas challenge the Pandavas to break a circular battle formation known as the Chakravyuha (see Wars of Hindu Mythology).
The Pandavas accept the challenge since they know that the knowledge of how to defeat such a formation is known to Krishna and Arjuna.
However, on that day, Krishna and Arjuna are dragged into fighting a war on another front with the Samsaptakas. Since the Pandavas have accepted the challenge already, they have no choice but to attempt to use young lad Abhimanyu, who has knowledge on how to break into the formation but none whatsoever regarding how to break out of it. To make sure that Abhimanyu does not get trapped in this endeavour, the remaining Pandava brothers decide that they and their allies will also break into the formation along with Abhimanyu and assist the boy in breaking out of it. It is important to note that the plan is hatched well after Arjuna and Krishna have been distracted away by the Samsaptaka army led by Susarma.
On the fateful day, Abhimanyu uses his skills to successfully break into the formation. The Pandava brothers and allies attempt to follow him inside the formation, but they are effectively cut off by Jayadratha, the Sindhu king, who makes use of a boon from Shiva to hold off all Pandavas except Arjuna for one day only. Abhimanyu is left to fend for himself against the entire Kaurava army.
When Abhimanyu commands his charioteer to lead his chariot towards Drona, the man is not happy to do so and raises objections. He requests the sixteen-year-old to take time to think about it before he begins the battle. He points out that Abhimanyu has grown up amidst great love and comforts and he is not a master of the battle arts as Drona is. Young Abhimanyu’s answer is disturbing to the reader of the epic and it speaks loudly of his underestimation of the mighty warriors on the Kaurava side and of his overestimation of himself, of his megalomania. Laughing aloud, he tells his charioteer: "What is this Drona or even the entire world of kshatriyas to me? I can fight Indra himself, mounted on his Airavata, along with all the gods! Why, I can fight in a battle even Lord Rudra himself, to whom the entire world of beings pays homage! This battle that I am going wage today does not bewilder me in the least.” Abhimanyu’s shocking words do not stop with these either. Continuing in the same vein he says: "This entire army of enemies is not equal to one sixteenth of my power. Why, even if I find in front of me in the battlefield my father Arjuna or my uncle himself, the mighty Vishnu who has conquered the whole universe, that wouldn’t frighten me.”
With no great joy in his mind, the poor charioteer takes his master forward. Abhimanyu breaks into the chakravyuha. In the mighty battle that follows with relentless ferocity for hours on end, he slaughters ordinary enemy warriors and mighty heroes alike, even as a whirlwind pulls up by their roots tiny bushes as well as mighty trees on its path
Abhimanyu fights valiantly single-handedly slaying several warriors who come his way including Duryodhana's son Laxman.Among the others who were killed are Karna’s younger brother, Ashmaka’s son, Shalya’s younger brother, Shalya’s son Rukmaratha, Drighalochana, Kundavedhi, Sushena, Vasatiya, Kratha and numerous other great warriors. He wounds Karna and makes him flee, makes Dushshasana faint in the battlefield so that he has to be carried off by others. Upon witnessing the death of his beloved son, Duryodhana is incensed and orders the entire Kaurava force to attack Abhimanyu. Continually frustrated in attempts to pierce Abhimanyu's armor, Karna on Dronacharya's advice shatters Abhimanyu's bow firing arrows from behind him. Thus disabled, his chariot breaks down shortly later, the charioteer and horses are killed, and all his weapons are laid to waste. He attempts then to fight off the bow wielding warriors sitting on horses, elephants at the same time with a sword and a chariot wheel as a shield. Dushasana's son engages in fierce hand to hand combat with Abhimanyu. Ignoring all codes of war, the Kauravas all fight simultaneously with him. He holds his own until his sword breaks and the remaining chariot wheel shatters into pieces. Abhimanyu gets killed shortly thereafter when Dushasana's son crushes his skull with a mace.
It is said that it is Abhimanyu's death that marks the end of the adherence to the rules of war. Krishna cites the despicable manner in which Abhimanyu was killed to incite Arjuna to kill Karna. This is cited as a reason to kill Duryodhana. Some say that this does not only apply to the particular war but marks the end of fair and nobly conducted wars.
News of the despicable acts committed on Abhimanyu reached his father Arjuna at the end of the day, who vows to kill Jayadratha the very next day by sunset, and failing to do so, commit suicide by self-immolation immediately.
The Kaurava army the next day places Jayadratha furthest away from Arjuna, and every warrior including the Samshaptakas (mercenaries to vow only to return from battle fields only upon victory else death) attempts to prevent Arjuna from reaching anywhere close to Jayadratha. Arjuna literally hacks through the Kaurava army and kills more than a hundred thousand soldiers and warriors in a single day. However, almost by sundown, Arjuna's chariot is still nowhere near Jayadratha's. Arjuna becomes despondent because he realizes that failure is imminent, and starts getting mentally prepared to self-immolate. Krishna being the almighty god uses his powers to temporarily to create an eclipse. The Kauravas and Pandavas alike believe that indeed the sun has set and the war stops according to the rules. Both sides come to watch Arjuna self-immolate. In his haste to see Arjuna's death, Jayadratha also comes to the front. Krishna sees the opportunity that he has effectively created, and the sun comes out again. Before the Kauravas can take corrective action, Krishna points out to Arjuna and asks him to pick up his Gandiva and behead Jayadratha. Arjuna's unerring arrows decapitate Jayadratha, and his vow to kill Jayadratha by sunset that day and avenge Abhimanyu's death is fulfilled. The reason for creating eclipse is also suggested at many places as a plot to save Arjuna from death, because Jayadratha had got a boon from his father that whoever would cause Jayadratha's head to fall onto earth would also die immediately. So Lord Krishna wanted everything to happen in this way so that Jayadratha would be on an easy aim. When Arjuna beheads Jayadratha, he does it so skillfully that the head falls straight into the lap of his father who was sitting under a tree. His father is shocked and stands up, causing Jayadratha's head to fall to earth. Thus his father is killed immediately.
Abhimanyu is the reincarnation of Varchas, the son of the moon god. When the moon god was asked to let his son incarnate himself on earth by the other devas, he made a pact that his son will only remain on earth for 16 years as he could not bear to be separated from him. Abhimanyu was 16 years old when he died in the war.
His son, Parikshita, born after his death, remains the sole survivor of the Kuru clan at the conclusion of the Mahābhārata war, and carries on the Pandava lineage.
Abhimanyu is often thought of as a very brave warrior on the Pandava side, willingly giving up his life in war at a very young age.