Bhishma was forced to participate and be on the side of the Kauravas in the Mahabharata War due to several factors rooted in his vows, his sense of duty (dharma), and his loyalty to the throne of Hastinapura. Here are the key reasons: Vow of Loyalty to Hastinapura: Bhishma had taken a solemn vow to protect and serve the throne of Hastinapura. This vow was made when he renounced his claim to the throne to ensure that his father, King Shantanu, could marry Satyavati. By this vow, Bhishma committed himself to the welfare of the kingdom, irrespective of who sat on the throne. Obligation to the Kuru Dynasty: As a member of the Kuru dynasty, Bhishma felt an obligation to support the ruling king. At the time of the war, Dhritarashtra was the king, and his son Duryodhana was the crown prince. Bhishma's duty to the Kuru lineage and the reigning monarch bound him to support them. Respect for Dhritarashtra's Authority: Despite knowing the unrighteousness of Duryodhana, Bhishma had