The British East India Company had been a trading presence on the Bengali coast since 1690. It operated a fortified factory at Calcutta (modern Kolkata) under nominal Mughal sovereignty. The Mughal empire was by 1750 in structural decline; the Bengali province of the empire was in practice an autonomous polity under the Nawab of Bengal.
In June 1756 the new young Nawab Siraj ud-Daulah (then 23) had marched on Calcutta in response to Company tariff evasions and military fortifications. He took the city. Approximately 150 British prisoners were confined overnight in the small guardroom of Fort William — the Black Hole of Calcutta — and 123 of them died of suffocation by morning. The contemporary British political reaction to the deaths was substantial.
The Company sent a punitive military force under Robert Clive — a 31-year-old former Madras Company writer who had risen to military command — to recapture Calcutta. He retook the city in January 1757 and then turned to reverse the political relationship with the Nawab.
The plot
Clive understood that direct military confrontation with Siraj ud-Daulah’s army of 50,000 was unwinnable for his 3,000-man Company force. The solution was to arrange a Bengali coup. Clive entered into secret negotiations with the Nawab’s senior military commander Mir Jafar and the financier Omichund, agreeing that they would betray Siraj at the next engagement in exchange for Mir Jafar’s elevation to the Bengali throne under Company protection.
The agreement involved bribes. Omichund had insisted on a 5 percent commission on the Bengal treasury; Clive produced two versions of the agreement — a real one without the Omichund commission, and a false one with it. Omichund was shown the false one. The duplicity was Clive’s own initiative.
The battle
The Company army of approximately 3,000 (800 European troops, 2,200 Indian sepoys, 10 field guns) met Siraj ud-Daulah’s army of approximately 50,000 at the mango grove of Plassey on the Hughli River on 23 June 1757.
A morning rainstorm soaked the Bengali ammunition stocks. The Company gunpowder was kept dry under tarpaulins. The weather disparity reduced the Bengali artillery effectiveness substantially.
The battle began at approximately 8 a.m. with Bengali artillery against the Company line. The Company artillery, functioning despite the rain, responded effectively. By approximately 11 a.m. the Bengali commander Mir Mardan — Siraj’s principal loyalist — had been killed by a Company artillery shell. Mir Jafar, commanding the Bengali centre, refused to engage and withdrew his contingent from the battle line.
The Bengali army’s right wing collapsed on Mir Mardan’s death. The remaining left-wing forces fought on for approximately two more hours and then disintegrated. Siraj ud-Daulah fled the battlefield on a camel.
The battle had lasted approximately three hours. Company casualties were 22 killed and 53 wounded. Bengali casualties were approximately 500 killed.
What followed
Mir Jafar was installed as Nawab of Bengal on 29 June 1757 under Company sovereignty. Siraj ud-Daulah was captured at Murshidabad on 2 July 1757 and was murdered the same night by Mir Jafar’s son. He was 24.
The financial transfer to the Company over the next year was approximately £2.5 million in immediate payments plus continuing annual tax revenue from Bengal. The Company’s previous commercial profits had averaged approximately £100,000 per year; the post-Plassey tax revenues exceeded £1 million per year by 1764.
The subsequent Battle of Buxar (October 1764) confirmed Company sovereignty over Bengal, Bihar, and Orissa through the defeat of a combined Mughal-Awadh-Bengali army. The 1765 Treaty of Allahabad transferred the diwani (revenue-collection rights) of these provinces formally from the Mughal emperor to the Company. The Company had become the de facto sovereign of approximately 40 million people.
What Plassey produced
The Bengal revenue from 1757 onwards funded the Company’s military expansion across India through the subsequent half-century. The Anglo-Mysore Wars (1767-1799), the Anglo-Maratha Wars (1775-1818), and the Anglo-Sikh Wars (1845-1849) extended Company control to all of mainland India by 1849.
The transfer of Indian wealth to Britain through this period — the “drain of wealth” that the Indian nationalist economist Dadabhai Naoroji would document in the 1870s — is estimated by modern economic historians at approximately £45 trillion in modern equivalent terms across the 190-year period from 1757 to 1947. The wealth transfer funded the early British Industrial Revolution and shaped the subsequent two centuries of Anglo-Indian relations.
Robert Clive returned to Britain in 1760 with personal wealth of approximately £300,000 (about £40 million in modern terms). He was elevated to the Irish peerage as Baron Clive of Plassey in 1762. He returned to India in 1765 as Company Governor of Bengal, made further fortune in the 1765-1767 administration, and then returned to Britain in 1767. He was the subject of parliamentary investigations in 1772-1773 for corruption; the investigations were inconclusive. He died of suicide (by laudanum and self-stabbing) at his London house in Berkeley Square on 22 November 1774, aged 49.
The cause of his suicide has been attributed to depression, chronic intestinal pain from opium addiction, and political-financial humiliation following the parliamentary investigations.
Mir Jafar lasted three years as Nawab before being deposed by the Company in 1760 and replaced with his son-in-law Mir Kasim. He was restored in 1763 and died in 1765, aged 73. The Mir Jafar name became the Bengali-language and Urdu-language synonym for treacherous betrayal — the linguistic usage has persisted for two and a half centuries.