
Civilisational history of Bangladesh previously known as East Bengal, dates back over four millennia, to the Chalcolithic. From the 14th century onward, it was ruled by the Bengal Sultanate, founded by king Shamsuddin Ilyas Shah, beginning a period of the country's economic prosperity and military dominance over the regional empires, which was referred by the Europeans as the richest country to trade with. Bengal Subah generated almost half of the empire's GDP and 12% of the world's GDP, larger than the entirety of western Europe, ushering in the period of proto-industrialization. Following the decline of the Mughal Empire in the early 1700s, Bengal became a semi-independent state under the Nawabs of Bengal, ultimately led by Siraj ud-Daulah. The borders of modern Bangladesh were established with the separation of Bengal and India in August 1947, when the region became East Pakistan as a part of the newly formed State of Pakistan following the end of British rule in the region. The records of Rajendra Chola I of the Chola dynasty, who invaded Bengal in the 11th century, affirms Govinda Chandra as the ruler of Bengal.