Dara Shikoh was the eldest son and the heir-apparent of the fifth Mughal Emperor Shah Jahan. He was favoured as a successor by his father and his sister Princess Jahanara Begum Sahib. In September 1657, the illness of emperor Shah Jahan triggered a desperate struggle for power among the four Mughal princes, though realistically only Dara and Aurangzeb had a chance of emerging victorious.

Despite strong support from Shah Jahan, who had recovered enough from his illness to remain a strong factor in the struggle for supremacy, and the victory of his army led by his eldest son Sulaiman Shikoh over his brother Shah Shuja in the battle of Bahadurpur, Dara was defeated by Aurangzeb and and brother Murad during the Battle of Samugarh, 13 km from Agra. Subsequently Aurangzeb took over Agra fort and deposed emperor Shah Jahan.

After this defeat Dara fled to Sindh and sought refuge under Malik Jiwan, an Afghan chieftain, whose life he had saved on more than one from the wrath of Shah Jahan. However, Malik betrayed Dara and turned him over to Aurangzeb’s army. Dara was brought to Delhi, placed on a filthy elephant and paraded through the streets of the capital in chains. Aurangzeb declared him a threat to the public peace and an apostate from Islam. He was assassinated and was beheaded, and his head was served to his father, Shah Jahan on a platter.

Dara had a deep interest in Sufism, and also attempted to find common language between Islam and Hinduism. Not able to find the answers he was looking for, Dara went on to study the Hindu Upanishads. The Mughal prince came to the conclusion that the “hidden book” mentioned in the Quran was none other than the Upanishads and believed that in order to understand the Quran, one needed to study the Hindu text. Dara even drew an equation between Adam and Brahma — a view which, according to historians, branded him as a heretic and ultimately led to his execution. Had Dara prevailed over Aurangzeb, the course of the history of the Indian subcontinent would have been different.

Reference:

http://www.indianage.com/search.php

http://en.wikipedia.org/wiki/Dara_Shikoh

http://dara-shikoh.blogspot.in/

http://www.ummid.com/news/2011/december/30.12.2011/historians_on_aurangzeb.htm