Battle of Plassey was fought in 1757 and Sirajuddaulah and his army was against The britishers, the britishers promised to make Mir Jafar the nawab of Bengal after defeating Sirajudaullah. So, During the battle Mir jafar and Britishers became one power and Sirajudaullah 's army was weak, hence defeating sirajudaullah Mir jafar was made the nawb of Bengal by the Britishers.
