Introduction

Bhishma was known by different names like Pitamaha , Gangaputra , Mahamahim , Devavrata , etc.  His childhood name was ' Devavrata ' . He was one of the 'Ashta Vasus ' ( meaning eight pillars which has withold the earth i.e Prithvi ) . He was one of the main characters of  Mahabharata who fought on Kurukshetra  from Kaurava's side and was their commander . He was very courageous and powerful .

Birth

Bhishma was born to river goddess Ganga and Kuru king Shantanu  . One day King Shantanu went on the bank of the river where he saw a very beautiful woman on the banks of the river . He approached her and expressed his love for her and put a proposal of marriage in front of her . The woman whom Shantanu saw was Ganga . She accepted his proposal but with a condition . She put the condition that the king will never stop her from doing anything and will never ask anything from her and if he does then she will leave him forever . The king accepted her condition and they got married . After some time , Ganga gave birth to a child . Soon after the birth of the child,  she took that child along with her and drowned that child in the river  . Like this she drowned her seven children soon after birth and king was unable to say something because of his promise that he gave to her at the time of marriage . But soon he got stressed for the heir of the kingdom after him . Now Ganga gave birth to the eighth child , soon after the birth of the eighth child she took that child too for drowning , as she was about to drown that child the king this time stopped her from doing so . Ganga reminded Shantanu of his promise but king who was so stressed about his heir and kingdom broke his promise . As king broke his promise so Ganga can no longer be with him , so she carried the baby along with him and told king that she will give him his son when there will be appropriate time for it . 

Reunion with his father 

After his departure from his wife and son , Shantanu was full of sadness . One day when he was walking along the banks of the river ganga then he saw that river water was getting shallow . To find out the reason he went forward along the bank and noticed that one boy has stopped the river water with his weapons . He was very shocked to see this. Then suddenly river Ganga appeared and told the king that he is his son ' Devavrata ' and father and son reunited . 

Bhishma Pratigya

One day Shantanu came to the forest on a hunting trip but got mesmerised by the musk fragrance that was coming from satyawati . Allured by that fragrance he followed her upto her home and fell in love with her from her first sight . Satyawati belonged to a fisherman community . She knew that king already has a son , so she but one condition that she will marry the king only when neither his son Devavrata ( i.e Bhishma ) nor Devavrata's son will sat on the throne . So for the sake of his father's happiness and for fulfilling his step-mother's  condition , Devavrata took an oath that he will remain celibate lifelong .  From this oath he was known by the name Bhishma and his pledge was known as "Bhishma Pratigya " .

Impressed  by his son's sacrifice , Shantanu granted Bhishma a boon of " Iccha Mrityu " i.e Bhishma could die out of his will .

Kurukshetra War 

Bound by his promise and loyalty towards Hastinapur , Bhishma had to join kauravas for Kurukshetra war . He was commander of Hastinapur's army . Due to the presence of  Bhishma in the war , it became almost difficult for Pandavas to win the battle . 

Death

On the eleventh day of war, Arjun with the help of Shrikhandi (Shrikhandini, who turned into Shrikhandi for one day through her austerity, just in order to take revenge from Bhishma of her previous birth as Amba). Bhishma had told Shrikhandini that whenever she will come in front of him , he won't raise his weapons against her. As a result, Arjun was able to pierce Bhisma with his arrows. Bhishma was lying on the bed of arrows but didn't die because of his iccha-mrityu boon. He kept lying on the bed of arrows till the last day of the war, seeing Mahabharata war happening in front of his eyes. After the war got over, he used his iccha-mrityu boon and died, giving blessings to Pandavas.