The Kurukshetra war was the greatest war ever fought for Dharma. With the support of Shri Krishna, the Pandavas were destined to win their fight against oppression, jealousy and greed of Duryodhan. However, before the start of the war, Shri Krishna mentions to Arjun and Duryodhan with a vow that he would not fight and yield a weapon in the war, but only give morale support to the side he was standing for. Knowing that Shri Krishna ‘s support itself was their greatest strength, Arjun humbly asks Shri Krishna to be his charioteer, while Duryodhan takes the entire Yadav army , thinking that Shri Krishna was unnecessary for him when he wouldn’t fight.
Before the war starts, the Pandavas come to the camp of Bhishma to seek his blessings in the war along with Shri Krishna. Being an ardent devotee of Shri Krishna, he understands the reason behind Shri Krishna’s vow, but being a warrior of the opposite side, he also challenges Shri Krishna that he would make Shri Krishna yield a weapon in the war for once. Shri Krishna smiles, but says nothing.
The war starts and both the sides fight relentlessly for victory. Although fighting for Dharma, it was not an easy task for the Pandavas as they had to fight great warriors like Bhishma, Dronacharya, Kripacharya and others to win. The wrath of Bhishma was especially very terrifying and none of the Pandava warriors or army could face his terrible arrows and fight him. This went on for few days, and Shri Krishna knew that unless Bhishma succumbed, the Pandavas hardly had a chance to win.
The next day, Arjun faces Bhishma, but is unable to take the vigour of Bhishma’s arrows. He fights hard to counter Bhishm’s arrows that were hurting not only Arjun, but Shri Krishna and the horses too. Suddenly, enraged at Bhishma’s war and in a fit of anger, Shri Krishna leaves the horses reins and jumps forward from the chariot. He then calls for his Sudarshan Chakr and moves forward to kill Bhishma. Seeing this action of Shri Krishna, Bhishma leaves his bows and arrows and bows to Shri Krishna and says that it is indeed a privilege that he dies in the hands of the Almighty himself. But Arjun rushes forward and stops Shri Krishna from attacking Bhishma, reminding Shri Krishna not to break his vow as it would be the defeat of Dharma. It is only when Arjun promises that he would defeat Bhishma that Shri Krishna goes and mounts the chariot again as a charioteer.
The real reason behind Shri Krishna getting ready to break up his vow was not hatred on Bhishma, but affection on him. Bhishma was his ardent devotee, and when his devotee took a pledge that he would make Shri Krishna yield a weapon in the war, it became the duty of Shri Krishna to fulfil the pledge of his dear devotee. Thus, Shri Krishna caused Bhishma’s actions to almost make him break his vow and yield a weapon. However, with the request of his another devotee Arjun, he again gives up the weapon and takes his position back as the charioteer of Arjun. The actions of Shri Krishna are always surprising, but when looked deeply, it was nothing but reciprocating for the love of his devotees in all ways possible.