The war of Mahabharata has begun after all negotiations by Lord Krishna and others to avoid it failed. The blind King (Dhritarashtra) was never very sure about the victory of his sons (Kauravas) in spite of their superior army. Sage Vyasa, the author of Mahabharata, wanted to give the blind king the boon of eyesight so that the king could see the horrors of the war for which he was primarily responsible. But the king refused the offer. He did not want to see the horrors of the war; but preferred to get the war report through his charioteer, Sanjaya. Sage Vyasa granted the power of clairvoyance to Sanjaya. With this power Sanjaya could see, hear, and recall the events of the past, present, and the future. He was able to give an instant replay of the eye witness war report to the blind King sitting in the palace.
Bhishma, the mightiest man and the commander-in-chief of the Kaurava’s army, is disabled by Arjuna and is lying on deathbed in the battleground on the tenth day of the eighteen day war. Upon hearing this bad news from Sanjaya, the blind King looses all hopes for victory of his sons. Now the King wants to know the details of the war from the beginning, including how the mightiest man, and the commander-in-chief of his superior army ¾ who had a boon of dying at his own will ¾ was defeated in the battlefield. The teaching of the Gita begins with the inquiry of the blind King, after Sanjaya described how Bhishma was defeated, as follows:
The King inquired: Sanjaya, please now tell me, in details, what did my people (the Kauravas) and the Pandavas do in the battlefield before the war started? (1.01)
Sanjaya said: O King, After seeing the battle formation of the Pandava’s army, your son approached his guru and spoke these words: (1.02) O Master, behold this mighty army of the Pandavas, arranged in battle formation by your other talented disciple! There are many great warriors, valiant men, heroes, and mighty archers. (1.03-06)

Introduction Of The Army Commanders

Also there are many heroes on my side who have risked their lives for me. I shall name few distinguished commanders of my army for your information. He named all the officers of his army, and said: They are armed with various weapons, and are skilled in warfare. (1.07-09)
Our army is invincible, while their army is easy to conquer. Therefore all of you, occupying your respective positions, protect our commander-in-chief. (1.10-11)