1905
The decision to effect the Partition of Bengal was announced in 7 July 1905 by the Viceroy of India, Lord Curzon. The partition took place on 16 October 1905 and separated the largely Muslim eastern areas from the largely Hindu western areas.
The provincial state of Bengal had an area of 189,000 mile and a population of nearly 78.5 million. It comprised to West Bengal with a Hindu majority and East Bengal and Assam with a Muslim majority. With the growing efforts of the Indian National Congress to secure the independence of India, Lord Curzon decided to address both these problems by partitioning Bengal into two entities, which would result in a Muslim-majority in the eastern half, and a Hindu-majority in the western half which will divide the population on religious grounds, quelling the Indian Independence Movement. But decision of Bengal Partition backfired and public at large opposed it and as a result Bengal was reunited in 1911 in an effort to appease Bengali sentiment.
Credit: Wiki