The Battle of Buxar in 1764 was primarily triggered by political tensions and ambitions among the major powers in India during that time. Here are the key circumstances that led to the battle:

1. Political Instability: The decline of the Mughal Empire in India had led to a power vacuum, with various regional powers vying for dominance. The weakening of central authority allowed local rulers and European colonial powers to expand their influence.

2. British Expansion: The East India Company, representing British interests in India, had been steadily expanding its control over Bengal, Bihar, and Orissa. This expansion alarmed other Indian powers, particularly the Nawab of Bengal, Siraj-ud-Daulah, who was defeated by the British in the Battle of Plassey in 1757.

3. Nawab of Oudh: Shuja-ud-Daula, the Nawab of Oudh, was also a significant player in this scenario. He allied with the Mughal Emperor Shah Alam II against the British, seeking to counter their growing influence.

4. Alliance Against the British: In 1763, Mir Qasim, who became the Nawab of Bengal after Siraj-ud-Daulah, formed an alliance with Shuja-ud-Daula and the Mughal Emperor Shah Alam II to challenge British dominance in the region.

5. Outbreak of Hostilities: Tensions escalated between the British East India Company and the coalition of Mir Qasim, Shuja-ud-Daula, and Shah Alam II. The British perceived this alliance as a threat to their interests and decided to confront them militarily.

6. Battle of Buxar: The decisive battle took place on October 22, 1764, near the town of Buxar (in present-day Bihar, India). The British forces, led by Major Hector Munro, defeated the coalition forces. This victory solidified British control over Bengal, Bihar, and Orissa, significantly expanding their territorial and political influence in India.

The Battle of Buxar marked a turning point in British colonial expansion in India, leading to increased British dominance and influence over Indian affairs in the following decades.