Siraj succeeded his maternal grandfather, Alivardi Khan as the Nawab of Bengal in April 1756 at the age of 23, but he was soon betrayed by his commander in chief Mir Zafar in the Battle of Plassey against the British.He died on 23 june 1757 at the age of 23-24 soon after annexing the throne of Bengal.After his death his kingdom was annexed by the British and Mir Zafar was made the ruler.