The Mahabharata is one of the two major Sanskrit Epics of ancient India.
The epic is also the longest epic in world literature.
This epic narratives of the Mahabharata family .There is a conflict of which branch of the family (the Kauravas and the Pandavas), will be the successor of the throne.

The Story of the Mahabharata :

King Pandu had five sons, called the the five Pandavas.
The blind king Dhritarashtra, the brother of king Pandu, had hundred sons.
King Pandu deceased very young and king Dhritarashtra became a regent.
Bhishma the Bharata patriarch. After the death of king Pandu he became the guardian of the Pandavas.

Dhritarashtra has a hundred sons. These are the Kaurava brothers, the eldest being Duryodhana, and the second Dushasana. The rivalry and enmity between them and the Pandava brothers, from their youth and into manhood leads to the Kurushetra war.
The Dhartarashtra party behaved viciously and brutally toward the Pandavas in many ways. From the time of their early youth onward. Their malice displayed itself most dramatically when they took advantage of the eldest Pandava, Yudhishthira, in a game of dice. Yudhishthira lost the game of dice and the Pandavas were forced to exile for 12 years.

The Pandavas spend twelve years in exile. At the end of their exile, they try to negotiate a return to Indraprastha. However, this fails because the leader of the Dhartarashtra party, Duryodhana, was unwilling to restore the Pandavas to their half of the kingdom when the thirteen years had expired. War becomes inevitable.
Both sides then called upon their many allies and two large armies arrayed themselves on the battlefield. Every kingdom had to choose a side. Bhishma the Bharata patriarch, choose the side of the Kauravas but his hart belonged to the Pandavas. The armies of Krishna choose also the side of the Kauravas.
Krishna Vasudeva was the cousin of both parties, but he was a friend and advisor to the Pandavas and served as Arjuna’s mentor and charioteer in the Great War.
Before the battle, Arjuna, seeing himself facing great-uncle Bhishma and his teacher Drona on the other side. Arjuna has doubts about the battle and he fails to lift his Gandiva bow. Krishna wakes him up to his call of duty in the famous Bhagavad-Gita section of the epic.

Pandavas won the eighteen day battle, but it was a victory that deeply troubled all. A lot of good men died. Bhishma, the Bharata patriarch, the Pandavas’ sons, their teacher Drona and several others died in the battle.
The Pandavas started to rule their kingdom but after a while they decided to renounce everything. Clad in skins and rags they retire to the Himalaya and climb towards heaven in their bodily form.