The Black Hole of Calcutta was a small dungeon in Fort William where British prisoners were held by the Nawab of Bengal, Siraj ud-Daulah, leading to the death of many due to overcrowding and poor conditions after the fort's capture on June 20, 1756. John Zephaniah Holwell, a prisoner, claimed that only 23 out of 146 survived the ordeal, although the accuracy of this figure has been contested. The incident triggered a military response from the British, with Robert Clive's forces defeating Siraj at the Battle of Plassey and leading to Siraj's downfall.