Gita teaches that all warfare in which man tries to slay his brothers is lamentable. But she does not teach that those who go to war, such as the Pandavas, in a righteous cause after having exhausted all means to preserve peace are blame worthy. The Duryodhanas of the world must be blamed for causing wars.
Gita primarily teaches a complete surrender (18:62, 65, 66) of egotism, but she does not teach a surrender of anything to evil powers, be they men, gods or devils. All of life is a struggle, and therefore one must struggle, struggle and struggle in one way or the other. But do not struggle against Truth, Love, and Joy. Struggle against lust, anger, greed, name and fame, jealousy, pride, vanity, arrogance, and deceptions.
Do not struggle against righteousness but against unrighteousness (Gita 2:31-37). He who goes to a battle, even for a righteous cause, must be prepared to be slain by the enemies who are or can be very powerful, (Gita 6:33-36) for that is the destiny of warriors like Mirabai who will not complain but in the end succeed.
A just war is never lost (Gita 2:37), and an unjust war is never won (Gita 2:16). He who is victorious must remember the instability of earthly things such as lust and greed that may bring him down again. If he moderates himself, extinguishes all hatred in his heart and lifts his down-trodden adversary up and says to him, "Come now and make peace and let us be brothers," he will gain a victory that is not a transient success, for its fruits will remain for ever.
Great are the victories in war, but he who has won over his ignorance, ego, pride, and vanity is the greatest warrior of them all. "The doctrine of conquest of the ego is not taught to destroy the souls of men but to preserve them. He who has conquered the ego (Gita 2:71) is more fit to live, to be successful and to gain victories than he who is a slave of the self.
He whose mind is free from illusion (Gita 2:2-3, 18:73) of the self will not fall in the battle of life. He whose intentions are righteousness and just will be successful in his enterprises, and his success will endure. He who harbors in his heart love of Truth will not die for he has drunk the waters of immortality. Struggle then, O man of lust and greed, courageously and fight your battles vigorously!
Truth will bless you with the ultimate eternal victory. You will at last be completely free from wars and loss or gain (Gita 2:38). That is the goal worth living for. Even animals live, eat, sleep, breath, raise their species and die. Think of the things that matter and do not forget your mother Truth in the deceptive colorful toys of this world (Gita 9:33).
-- Swami Radhanandaji