During the rule of Mughals when the Hindus were forced to convert to Islam and there was no one who could object to it.

Then , kashmiri pandits came to guru sahib because auranzeb was forcefully trying to change their religion.

After hearing their appeals guru sahib said that some (mahapurakh)have to sacrifice his life to stop all this things.Bal Gobind Rai ( guru Gobind Singh ji) sitting next to him said that ( aapse bda mahapurakh kon hoga) Guru sahib smiled and was happy to see the bravery of his young son

Guru ji addressed the Pandits, "Go and tell Aurangzeb that if he can convert Guru Tegh Bahadar to Islam, they will all convert. Otherwise he should leave them alone.

It was Guru Teg Bahadur who came forward and objected to his unjustics and asked Aurangzeb to stop this and offered his head saying, “If you convert me, all the Hindus will become Muslims if you can’t, stop your high headedness.” This was a straight challange from Guru Teg Bahadur to Aurangzeb.

So to force Guru Teg Bahadur to convert to Islam he tortured him but failed and in frustration killed him at Chandni Chowk Delhi, where now in his memory there stands a Gurudwara Sis Ganj Sahib. Because he sacrificed his life for protecting the Hindus from his tyranny, that’s why he is known as “Hind di chaadar” - 'Sheild of India'.