Fought 23rd June 1757 between the British forces of the East India Company and the forces of the Nawab of Bengal at Plassey Grove, a small village and mango grove located between Calcutta and Murshidabad; the British victory providing a major breakthrough for British influence on the sub-continent, paving the way for the establishment of British rule in India.
The old Mughal empire of India was in decline, and in the resulting power vacuum a number of native Indian rulers stepped in such as the Alivardi Khan, who by 1740 had become to all intents and purposes the ruler or Nawab of an independent Bengal. It also allowed the European powers to establish a foothold on the sub-continent, at least in the form of their trading companies; the British East India Company, the Dutch Verenigde Oostindische Compagnie and the French Compagnie des Indes.
In 1756 Alivardi Khan died leaving his widow Ghasiti Begum and grandson Siraj Ud Daulah locked in a power struggle for control of Bengal; despite the support of the British, Ghasiti Begum lost out to Siraj Ud Daulah who succeeded in making himself Nawab.
The Seven Years War was also in progress, and both the British and the French were keen to drive each other out of India. The strengthened the fortifications of Fort William at Calcutta to protect it against any French assaults; Siraj Ud Daulah took exception to this as it had been done without his permission. With this in mind and the prior British support for his rival, on 20th June 1756, he attacked and captured both Fort William and Calcutta. Many of the British who were taken prisoner during the assault were imprisoned in a dark airless room, later known as the Black Hole of Calcutta, in which most of the prisoners died.
In response to this 'atrocity' the British East India Company sent a relief force under Robert Clive which retook Calcutta on the 2nd January 1757. Siraj Ud Daulah was forced under the resulting treaty of Alinagar to restore the trading priviliges of the East India Company and pay reparations.
The battle itself
Siraj Ud Daulah wasn't happy with this reverse, delayed paying the necessary reparations and began courting the French, and so the British, or more particularly Robert Clive, decided to be rid of him. The British captured the French settlement of Chandernagore and casting around for allies came across Mir Jafar, the disaffected uncle of Siraj Ud Daulah who also happened to be commander of the Nawab's forces.
Secure in the knowledge that significant French intervention was unlikely and with Mir Jafar in his back pocket, Robert Clive set out from Chandernagore on the 13th June 1757 with a force of some three thousand and eight cannon to deal with Siraj Ud Daulah. On the 22nd they reached Plassey Grove and made contact with the Nawab's forces of some fifty thousand in all together with over forty pieces of cannon.
The battle itself took place the next day; during the morning the Bengal forces shelled the British, who secure under the cover of the mango trees and the surrounding mud banks suffered only minor casualties. At midday the Bengalis retired to their camp and the British advanced to take some high ground, began shelling the Bengali forces. Having created a certain amount of confusion amongst the enemy forces, the British then stormed their camp, scattered their forces, chased them for six miles, captured their cannon and killed around five hundred.
As a battle it didn't amount to much. Although Siraj Ud Daulah may well have been confident of victory, given the overwhelming superiority of numbers he enjoyed (plus French assistance in managing the cannon) in reality most of his forces had already been bribed to offer no resistance; the result of the battle was really a forgeone conclusion. The fact that there were only losses of five hundred out of fifty thousand on the losing side shows what little actual fighting took place.
Siraj Ud Daulah didn't survive this defeat and was assassinated at his palace in Murshidabad; Mir Jafar received his reward and became Nawab in his place.
It made the East India Company effective masters of Bengal, within a few years the provinces of Bengal, Orissa and Bihar were in their hands, and British rule in India was well and truly established. It made Robert Clive a very rich man indeed as the pay off from Mir Jafar amounted to £234,000 together with an annuity of £30,000. (In 1757 pounds; £££'s millions in current money.)
The battle still excites controversy today; Indian historians such as Jawaharlal Nehru get very high and mighty about the whole affair accusing Robert Clive of winning only by means of inducing treason, although quite why paying off your enemies is more morally reprehensible than killing them somehow escapes me.
Although Clive's conduct is very much open to criticism (he deceived Omichund, a go between himself and Mir Jafar by means of a forged agreement and thereby cheated him out of the £300,000 that he was promised) and was clearly motivated by a certain amount of greed. (He was an accountant.) Although the Nawab Siraj Ud Daulah was no better, quite prepared to make a treaty with the British one minute, then break it to do a deal with the French the next. Basically, eighteenth century India was a rich country (at least in the sense that the rulers were adept at accumulating wealth at the expense of the rest) and everyone, Clive, Siraj and Omichund wanted their cut.
Oh yes, and Britain ended up ruling India for a couple of centuries.
Articles on the battle at www.bengalweb.com/hist/calhis1a.html and www.bangalinet.com/calcutta2.htm, Clive's own account of the battle from Oliver J. Thatcher, ed., The Library of Original Sources, (Milwaukee: University Research Extension Co., 1907), Vol. VII: The Age of Revolution, pp. 59-64 located at www.fordham.edu/halsall/mod/1757plassey.html and David Landes, The Wealth and Poverty of Nations (WW Norton & Co Inc, 1998)