First of all let us get clarity about HINDUISM .
'Hinduism' is actually very-very little of a religion, if you talk of the essence of Hinduism. The more you call Hinduism, a religion, the more you are destroying the real thing. So, Hinduism is great only as long as it is not a religion. The moment you say, 'Hindu-ism is great', it's gone, finished.
Hinduism is not at all a religion in the sense Christianity and Islam are religions. The Upanishads do not propagate a religion at all. Are you getting it? How can you follow a religion after reading Ribhu Gita? Gone, finished! There is no question of religion. Yes, if this religiousness can be called 'Hinduism', then it is alright. Then it is alright.
A real Hindu does not have any religion. To go beyond all religions is to be a Hindu. So, there are religions who are on one plane, and then there is Sanaatan Dharma , which is another dimension. It is Sanaatan Dharma; the eternal religiousness. It is not a religion.
Sanaatan Dharma is awakened intelligence, also called 'Swadharma'. You know what you must do at any point, because you know who you are, that is Swadharma. Now, you don't need a dharma because you know Swadharma, that is Sanaatan dharma; Swadharma. That is what Krishna has talked about.
What has happened is that because there are other religions, so the so-called Hindus also find it necessary to find what is their religion. 'Everybody has a religion, what is my religion?' Son, a Hindu actually doesn't have a religion, and that's such good news. He has been born and brought up in the shadow of the saints, and that is why he does not have a religion. It's like everybody is walking on the crutches and the healthy child asks, 'Where are my crutches?' You don't have crutches, son. You don't have crutches.
For your question about war:-
"Misplaced desire is suffering, so is misplaced renunciation. Misplaced war is bad, so is misplaced peace.
ALL IS GOOD, AT ITS PROPER PLACE."
When Krishna says, 'Swadharme nidhanam shreya (स्वधर्मे निधनं श्रेयः)', he is not talking about Hinduism. He is talking about the action of Intelligence.