Read the story of Shikhandini from Mahabharata. It is a famous and poignant story. She was a women (Amba) abducted by Bhishma, the Kaurava warrior, for marriage to his nephew. But before the marriage could have taken, the nephew died. The person who she earlier wanted to marry refused to accept her. Shikhandini asked a sage to give her a new life as a male warrior so that she could take her revenge from Bhishma, because she knew Bhishma would not fight with her if she remained in the form of a female. That is not considered fair in Hinduism. For that she jumped into a fire sacrifice. The sage did give her a new life as a warrior but fumbled in the mantras to change her sex. When Shikhandini saw that she was still a woman, she comlained. The sage corrected his mistake by changing her sex to that of a male (how easy is that in mythology
). In the great Mahabharata war, Arjuna hid behind Shikhandi to shoot an arrow at Bhishma. Though that too was unfair in Hinduism, Krishna advised Arjuna to go ahead with it, because there was no other way Bhishma could be killed. Bhishma saw all that, but he felt guilty about his abduction of Amba wanted to pay for his error. He let Arjuna shoot him from behind Shikhandi, though he had power to do so.