Five Gurus

Bhishma is a very strong character in Mahabharata. He was son of Ganga and Shantanu. His childhood name was Devavrata. During his childhood, Devavrata was taught political science and other subjects by

1. Brihaspati and 
2. Sukracharya, gurus of the Devas and Asuras respectively; 
3. Vedas and religious scriptures by the sage Vasishtha; 
4. Sage Markandeya was his spiritual guru. 
5. On Ganga's persuasion, Devavrata was taught martial arts, military sciences and the use of weapons by Parashurama.