SB 1.15.15
yo bhisma-karna-guru-salya-camusv adabhra-
rajanya-varya-ratha-mandala-manditasu
agrecaro mama vibho ratha-yuthapanam
ayur manamsi ca drsa saha oja arcchat
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
It was He only who withdrew the duration of life from everyone and who, in the battlefield, withdrew the speculative power and strength of enthusiasm from the great military phalanx made by the Kauravas, headed by Bhisma, Karna, Drona, Salya, etc. Their arrangement was expert and more than adequate, but He [Lord Sri Krsna], while going forward, did all this.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The Absolute Personality of Godhead, Lord Sri Krsna, expands Himself by His plenary Paramatma portion in everyone’s heart, and thus He directs everyone in the matter of recollection, forgetfulness, knowledge, the absence of intelligence and all psychological activities (Bg. 15.15). As the Supreme Lord, He can increase or decrease the duration of life of a living being. Thus the Lord conducted the Battle of Kuruksetra according to His own plan. He wanted that battle to establish Yudhisthira as the Emperor of this planet, and to facilitate this transcendental business He killed all who were on the opposite party by His omnipotent will. The other party was equipped with all military strength supported by big generals like Bhisma, Drona and Salya, and it would have been physically impossible for Arjuna to win the battle had the Lord not helped him by every kind of tactic. Such tactics are generally followed by every statesman, even in modern warfare, but they are all done materially by powerful espionages, military tactics and diplomatic maneuvers. But because Arjuna was the Lord’s affectionate devotee, the Lord did all this Himself without personal anxiety by Arjuna. That is the way of the devotional service to the Lord.