The topics discussed by Dhṛtarāṣṭra and Sañjaya, as described in the Mahābhārata, form the basic principle for this great philosophy. It is understood that this philosophy evolved on the Battlefield of Kurukṣetra, which is a sacred place of pilgrimage from the immemorial time of the Vedic age. It was spoken by the Lord when He was present personally on this planet for the guidance of mankind.
(Bhagavad-Gita-----1:1-----purport).

The word dharma-kṣetra (a place where religious rituals are performed) is significant because, on the Battlefield of Kurukṣetra, the Supreme Personality of Godhead was present on the side of Arjuna. Dhṛtarāṣṭra, the father of the Kurus, was highly doubtful about the possibility of his sons' ultimate victory.
(Bhagavad-Gita-----1:1-----purport).

He did not want a compromise between the cousins and brothers, and he wanted to be sure of the fate of his sons on the battlefield. Because the battle was arranged to be fought at Kurukṣetra, which is mentioned elsewhere in the Vedas as a place of worship—even for the denizens of heaven—Dhṛtarāṣṭra became very fearful about the influence of the holy place on the outcome of the battle. He knew very well that this would influence Arjuna and the sons of Pāṇḍu favorably, because by nature they were all virtuous. Sañjaya was a student of Vyāsa, and therefore, by the mercy of Vyāsa, Sañjaya was able to envision the Battlefield of Kurukṣetra even while he was in the room of Dhṛtarāṣṭra. And so, Dhṛtarāṣṭra asked him about the situation on the battlefield.
(Bhagavad-Gita-----1:1-----purport).

Droṇācārya knew this perfectly well, and yet as a liberal brāhmaṇa he did not hesitate to impart all his military secrets when the son of Drupada, Dhṛṣṭadyumna, was entrusted to him for military education. Now, on the Battlefield of Kurukṣetra, Dhṛṣṭadyumna took the side of the Pāṇḍavas, and it was he who arranged for their military phalanx, after having learned the art from Droṇācārya. Duryodhana pointed out this mistake of Droṇācārya's so that he might be alert and uncompromising in the fighting.
(Bhagavad-Gita-----1:3-----purport).

The Battle of Kurukṣetra, being the will of the Supreme, was an inevitable event, and to fight for the right cause is the duty of a kṣatriya. Why should Arjuna be afraid of or aggrieved at the death of his relatives since he was discharging his proper duty? He did not deserve to break the law, thereby becoming subjected to the reactions of sinful acts, of which he was so afraid.
(Bhagavad-Gita-----2:27-----purport).

The Supreme is the Personality of Godhead for the devotees, and liberation for the impersonalist. A person, therefore, acting for Kṛṣṇa, or in Kṛṣṇa consciousness, under proper guidance and without attachment to the result of the work, is certainly making progress toward the supreme goal of life. Arjuna is told that he should fight in the Battle of Kurukṣetra for the interest of Kṛṣṇa because Kṛṣṇa wanted him to fight. To be a good man or a nonviolent man is a personal attachment, but to act on behalf of the Supreme is to act without attachment for the result. That is perfect action of the highest degree, recommended by the Supreme Personality of Godhead, Śrī Kṛṣṇa.
(Bhagavad-Gita-----3:19-----purport).

Being a great devotee of the Lord, he was transcendentally situated, but because he was the king of Mithilā (a subdivision of Bihar province in India), he had to teach his subjects how to perform prescribed duties. Lord Kṛṣṇa and Arjuna, the Lord's eternal friend, had no need to fight in the Battle of Kurukṣetra, but they fought to teach people in general that violence is also necessary in a situation where good arguments fail. Before the Battle of Kurukṣetra, every effort was made to avoid the war, even by the Supreme Personality of Godhead, but the other party was determined to fight. So for such a right cause, there is a necessity for fighting. Although one who is situated in Kṛṣṇa consciousness may not have any interest in the world, he still works to teach the public how to live and how to act.
(Bhagavad-Gita-----3:20-----purport).

Since everything is in full opulence in the Personality of Godhead and is existing in full truth, there is no duty for the Supreme Personality of Godhead to perform. One who must receive the results of work has some designated duty, but one who has nothing to achieve within the three planetary systems certainly has no duty. And yet Lord Kṛṣṇa is engaged on the Battlefield of Kurukṣetra as the leader of the kṣatriyas because the kṣatriyas are duty-bound to give protection to the distressed. Although He is above all the regulations of the revealed scriptures, He does not do anything that violates the revealed scriptures.
(Bhagavad-Gita-----3:22-----purport).

A man of controlled senses cannot be offensive to anyone. One may ask, "Why then was Arjuna offensive (in battle) to others? Wasn't he in Kṛṣṇa consciousness?" Arjuna was only superficially offensive because (as has already been explained in the Second Chapter) all the assembled persons on the battlefield would continue to live individually, as the soul cannot be slain. So, spiritually, no one was killed on the Battlefield of Kurukṣetra. Only their dresses were changed by the order of Kṛṣṇa, who was personally present. Therefore Arjuna, while fighting on the Battlefield of Kurukṣetra, was not really fighting at all; he was simply carrying out the orders of Kṛṣṇa in full Kṛṣṇa consciousness. Such a person is never entangled in the reactions of work.
(Bhagavad-Gita-----5:7-----purport).

But anyone who can understand the plan of the Supreme Lord and cultivate Kṛṣṇa consciousness is most intelligent. The creation and destruction of the cosmic manifestation are under the superior guidance of God. Thus the Battle of Kurukṣetra was fought according to the plan of God. Arjuna was refusing to fight, but he was told that he should fight in accordance with the desire of the Supreme Lord. Then he would be happy. If one is in full Kṛṣṇa consciousness and his life is devoted to the Lord's transcendental service, he is perfect.
(Bhagavad-Gita-----11:33-----purport).

Arjuna, after hearing from Kṛṣṇa about the outcome of the Battle of Kurukṣetra, became enlightened, and as a great devotee and friend of the Supreme Personality of Godhead he said that everything done by Kṛṣṇa is quite fit.
(Bhagavad-Gita-----11:36-----purport).

Arjuna understood herein that when the Battle of Kurukṣetra was being concluded, in outer space there were present many demigods, siddhas, and the intelligentsia of the higher planets, and they were observing the fight because Kṛṣṇa was present there.
(Bhagavad-Gita-----11:36-----purport).

The devotee does not desire any achievement other than pleasing the Supreme Personality of Godhead. His life's mission is to please Kṛṣṇa, and he can sacrifice everything for Kṛṣṇa's satisfaction, just as Arjuna did in the Battle of Kurukṣetra. The process is very simple: one can devote himself in his occupation and engage at the same time in chanting Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare/ Hare Rāma, Hare Rāma, Rāma Rāma, Hare Hare. Such transcendental chanting attracts the devotee to the Personality of Godhead.
(Bhagavad-Gita-----12:6-7-----purport).

In the beginning of Bhagavad-gītā, Dhṛtarāṣṭra inquired from his secretary Sañjaya, "What happened on the Battlefield of Kurukṣetra?" The entire study was related to the heart of Sañjaya by the grace of his spiritual master, Vyāsa. He thus explained the theme of the battlefield. The conversation was wonderful because such an important conversation between two great souls had never taken place before and would not take place again. It was wonderful because the Supreme Personality of Godhead was speaking about Himself and His energies to the living entity, Arjuna, a great devotee of the Lord.
(Bhagavad-Gita-----18:74-----purport).