Siraj-ud-Daulah became the Nawab of Bengal in 1756, and he was not the puppet ruler which the company wanted, so they promised one of the rivals of Siraj-ud-Daulah to help become nawab.
The agitated Siraj asked the company to stop interfering in the political affairs, stop fortification and pay the revenue taxes.
After failed negotiations, Siraj-ud-Daulah with his army sieged the factory English factory atKasim Bazar, disarmed the officials and locked the warehouse and moved forward to siege the Fort Williams.
More than half of the prisoners died in the warehouse on the night of June 20, 1756. This event is known as Black Hole of Calcutta.
This incident made thecompany sent its army under the leadership of Robert Clive, after many negotiations, finally in 1757, the battle of Plassey took place at the place called Palashi on the banks of Hooghly River, Calcutta.
The war continued for 7 years (1757-1763), and finally, Siraj-ud-Daulah got defeated and assassinated by British due to deceit from his commander in chief Mir Jafar Ali, whom Clive lured to give the position of the nawab.
Battle of Plassey was an unfoughtand the first victory for the British in India.