What was the main reason for the Mahabharata war?

 

There was enmity between Kauravas and Pandavas and all the elders of Kuru dynasty knew that. However, after the marriage of the Pandavas with Draupadi, Shri Krishna and others impressed upon Dhritarashtra to give Pandavas share in the Kingdom. Hence, Pandavas were given their land with Indraprastha as their capital. Pandavas developed their kingdom depending upon their own strength.

Hence, thereafter there were no quarrels between Kauravas and Pandavas.

However, after attending to the Rajasuya Yagna, Duryodhana was overwhelmed with jealousy and impressed upon Dhritarashtra to invite Yudhisthira to game of dice. Duryodhana knew well that though Yudhisthira was fond of game of dice, he was not an expert in that game.

Then, Dhritarashtra send invitation to Yudhisthira for game of dice, through Vidura. The following is the conversation between Yudhisthira and Vidura.

[y]
dyūte kṣattaḥ kalaho vidyate; naḥ kaś vai dyūtaṃ rocayed yudhyamānaḥ
kiṃ vā bhavān manyate yuktarūpaṃ; bhavadvākye sarva eva sthitāḥ sma

"Yudhishthira said,--'O Kshatta, if we sit to a match at dice, we may quarrel. What man is there, who knowing all this, will consent to gamble? What dost thou think fit for us? We all are obedient to thy counsels.'

[vi]
jānāmy ahaṃ dyūtam anarthamūlaṃ; kṛtaś ca yatno 'sya mayā nivāraṇe
rājā tu māṃ prāhinot tvatsakāśaṃ; śrutvā vidvañ śreya ihācarasva

"Vidura said,--'I know that gambling is the root of misery, and I strove to dissuade the king from it. The king, however, hath sent me to thee. Having known all this, O learned one, do what is beneficial.

[y]
ke tatrānye kitavā dīvyamānā; vinā rājño dhṛtarāṣṭrasya putraiḥ
pṛcchāmi tvāṃ vidura brūhi nas tān; yair dīvyāmaḥ śataśaḥ saṃnipatya

"Yudhishthira said,--'Besides the sons of Dhritarashtra what other dishonest gamblers are there ready for play? Tell us, O Vidura, who they are and with whom we shall have to play, staking hundreds upon hundreds of our possessions.'

[vi]
gāndhārarājaḥ śakunir viśāṃ pate; rājātidevī kṛtahasto matākṣaḥ
viviṃśatiś citrasenaś ca rājā; satyavrataḥ purumitro jayaś ca

"Vidura said,--'O monarch, Sakuni, the king of Gandhara, an adept at dice, having great skill of hand and desperate in stakes, Vivingati, king Chitrasena, Satyavrata, Purumitra and Jaya, these, O king, are there.'

[y]
mahābhayāḥ kitavāḥ saṃniviṣṭā; māyopadhā devitāro 'tra santi
dhātrā tu diṣṭasya vaśe kiledaṃ; nādevanaṃ kitavair adya tair me

"Yudhishthira said,--'It would seem then that some of the most desperate and terrible gamblers always depending upon deceit are there. This whole universe, however, is at the will of its Maker, under the control of fate. It is not free.

nāhaṃ rājño dhṛtarāṣṭrasya śāsanān; na gantum icchāmi kave durodaram
iṣṭo hi putrasya pitā sadaiva; tad asmi kartā vidurāttha māṃ yathā

O learned one, I do not desire, at the command of king Dhritarashtra to engage myself in gambling. The father always wisheth to benefit his son. Thou art our master, O Vidura. Tell me what is proper for us.

na cākāmaḥ śakuninā devitāhaṃ; na cen māṃ dhṛṣṇur āhvayitā sabhāyām
āhūto 'haṃ na nivarte kadā cit; tad āhitaṃ śāśvataṃ vai vrataṃ me

Unwilling as I am to gamble, I will not do so, if the wicked Sakuni doth not summon me to it in the Sabha? If, however, he challenges me, I will never refuse. For that, as settled, is my eternal vow."

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Please note the last statement of Yudhisthira.

If, however, he (Sakuni) challenges me, I will never refuse. For that, as settled, is my eternal vow."

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So, it is clear from the above that Yudhisthira had taken vow that if anyone challenges him for game of dice, he would not refuse. And, he accepted the invitation, in spite of understanding the consequences of playing the game of dice.

—-

Further, Yudhisthira was not an ordinary King. He had become an emperor, by performing Rajasuya Yagna.

So, apart from being the eldest among Pandavas, he was the ruler of the country. Thus, he should have applied more caution whether to attend to the game of dice, as he has responsibility towards his brothers and wives as well as the people under his rule.

Instead of exercising caution, he had succumbed to weakness towards the game of dice. Inspite of knowing full well of the consequences, he decided to play.

He was solely responsible for the war. That is my understanding.

Hence, it is the mistake of Yudhisthira, to accept the invitation for the game of dice that led to the great war.