Let me narrate a less known story from the Mahabharata, Udyoga Parva.
Bhishma, the Grand sire of the Kuru Dynasty, was born as Devavrata, for Shantanu .
When Shantanu wanted to marry Ganga who was in the earth,due to Curse by Devendra on her and The Ashta(8) Vasus who were to be born as her children only to be killed by her as soon as they are born.
The Eighth to be born was Devavrata, who later would be known as Bhishma.
For more read the Mahabharata.
To enable Shantanu to marry the daughter of a fisherman Parimala Gandhi,, Devavrata vowed that he would never marry to prevent a stake, a claim for the throne through his offsprings.
For this he was acclaimed by the Devas as ‘Bhishma’ the One who does what is not possible.
Bhisma remained as a Naishtika Brahmachari till his death ( one who does not allow his semen to fall)
Bhishma, in his effort to get his step brothers married, was caught in a situation where he had to marry Amba, daughter of the King of Kasi for he attended the Swayamvara and Amba chose him: Bhisma refused to marry Amba explaining to her of his vow and the fact that he attended the Swayamvara only to choose a Bride for his step brother,Amba did not agree.
Parasurama, who is an Avatar of Vishnu, vowed to root out the Kshatriyas by engaging them in war and he vowed that he would never teach the Dhanur Vidya to Kshatriyas.
This is because his father Jamadagni was killed by Karthaveeryujana .
Be that as it may be, to go on..
Bhishma was an exception, he was taught the Dhanur Vidya by Parasurama Himself( I do not have a satisfactory explanation for this, excepting my guess that Bhishma was taught by Parasurama before Parasurama took his vow;even this is faulty for in Ramayana, Lord Rama was challenged by Parasurama to fight him because his vow him, mind you Ramayana took place in Treta Yuga while Mahabharata took place on The Dwapara Yuga)
Now in this instance Parasurama, urged by Amaba fought furiously with Bhishma.
Bhishma remained undefeated.
Parasurama had to leave the field because Narada and Ganga stood in the middle of the furious battle.
Prior to the battle, Bhisma tells Parasurama,
‘You are my Guru.
You know my Pratigya, Vow,
Yet you are forcing me to marry Amba , leaving me no choice to fight you.
Let me tell you, I am your disciple and I revere you, and My strength is reinforced by my Guru Bhaktii.
may be you have won the other Kshatriyas earlier,
This Bhisma was not born then”
‘Na Bhayannapynukro saaanthartha…..Rama na samyaihi( Mahabharata, Udyoga Parva-17)
I shall post some more least known stories from the Hindu Epics and Puranas.
*Amba after her suicide; was reborn as Sikandi ; as Bhishma knew that she was a woman in earlier birth he vowed not to bear arms against Sikandi.
Krishna used Sikandi as a shield and had Arjuna kill Bhishma!