Shantanu, king and father of Bheeshma the great grandfather of the Pandavas and Kauravas in the Mahabharata, is a familiar figure. The stories about his infatuation for Satyavati and his marriage to Ganga and his son Devavrata who came to be known as Bheeshma for the terrible vow that he undertook are also common knowledge. But this is a story about Shantanu before he met Satyavati and before his son swore to lifelong celibacy, one that is not as universally known as the others.
The story recorded in the Vishnu Purana is told by the sage Parashara, who fathered Vyasa (author of the Mahabharata among other things) with Satyavati. The sage, in a way set the ball rolling for the chain of events that led to the rise and fall of the Kuru dynasty. Over to him.
Shantanu was the second son of King Pratapi. His elder brother, the eldest son of the king and the rightful heir to the throne was Devapi. But Devapi had renounced the royal life at a very young age and the kingdom was handed over to Shantanu after his father's death.
Under his rule, the kingdom suffered a long drought. Some say it went on for 12 years and a great famine struck the people. The king reached out to sages and learned men for an answer; they told him that the people were being punished for the sins of their king. Shantanu had taken over the reins of a kingdom that rightfully belonged to his brother, Devapi, and hence nature had turned its wrathful eye upon him.
Eager to set things right, Shantanu asked his trusted and wise minister Ashmasuri to help bring Devapi back. The minister, in his wisdom, sent a preacher to the forest to prepare the royal scion for his return. The preacher however, upon reaching the forest, decided to preach against the Vedas. He taught Devapi all things that were considered sinful in the Vedas and words that carried foul feelings and hateful intent.
In a few months, Shantanu took along an entourage to visit his brother and lead him back to the kingdom. But when they reached the forest, they were taken aback to find him mouthing profanities. This made Devapi a sinner and an unfit king according to the Vedas. So Shantanu returned to his kingdom, this time as the rightful heir to the throne and nature restored her benign gaze upon him and his people.