Both parts used to be united , although historically part of India ; today West Bengal is part of India and East Bengal is Bangladesh . In spite of a last ditch effort to form a United Bengal , when India gained independence in 1947 , Bengal was partitioned along religious lines . The western part went to India ( and was named West Bengal ) while the eastern part joined Pakistan as a province called East Bengal ( later renamed East Pakistan , giving rise to Bangladesh in 1971 ) .