The context of VishnuSahasranamam in Bharatham is like this.
Bheeshma Pitamaha is defeated and covered all over his body by the arrows sent by Arjuna in the war and he is just lying in the battlefield in a bed of arrows awaiting death.. because he has the power to choose the time of death, and he wants to leave his mortal body when Uttarayanam starts..
Meanwhile the Pandavas win the battle, Yudhistira becomes king.. Krishna is present to assist in establishing the Pandavas securely in the throne. In spite of many discussions with Krishna and others, all feel that the final authority in law, politics and Dharma is Bheeshma alone, and so the King, accompanied by his brothers and also the Blessed Lord Krishna, pay a visit to the dying Patriarch Bheeshma, and the Grand old man willingly shares all his knowledge with the Emperor that too in the presence of the Eternal Being Krishna standing there is great reverence to the elderly warrior.
After discussing statecraft and law, the discussion turns to the means available for human beings to attain welfare in the earthly life as well as life of eternity thereafter..
Bheeshma lists the most important thousand names of Lord Narayana,, present before Him as Krishna the son of Devaki, and declares that chanting or contemplating on these thousand names is the ultimate for a human being in spiritual and temporal life..
The greatness of the mantra is that the dying old man is stating with ultimate faith and authenticity about the glory of the Supreme being, who just stands before him like an obedient child and listens..
And Bheeshma does not fail to deliver the final punch..."रथाङ्गपाणिरक्षोभ्यःसर्वप्रहरणायुधः rathaangapaanir akshobhyaH sarvapraharanaayuthaH --the man who wears the wheel of a chariot ready to strike...
Yes, Krishna has promised that He would never wield a weapon for strike in the Bharatha war, and Bheeshma was keen that the lord should be forced to wield the weapon..
In a fierce battle with Arjuna, where Krishna was the Charioteer, Bheeshma would disarm Arjuna and force Krishna to charge ahead with the wheel of a chariot in hand to attack Bheeshma and protect Arjuna.. and Bheesma withdraws at that moment in deference to the Blessed Lord Krishna..
In fact, it was just because Krishna wanted to admit defeat and break a promise for the sake of a pure devotee that such a thing happened..
It was the zenith of glory for Bheeshma and the old man concluded the Vishnusahasranamam, calling Krishna as the one who wielded the chariot wheel in battle, breaking a promise.