Modern Bengal produced the reform movements that shaped how Hinduism was argued about globally, and then was divided twice.
The Brahmo Samaj, founded in Calcutta in 1828, rejected image worship and caste and read the Upanishads as monotheist scripture; the Bengal Sati Regulation of 1829, which criminalised widow burning in the presence of British authority, belongs to the same reforming milieu and to the arguments in it about which practices scripture actually required. Later in the century Ramakrishna, a temple priest at Dakshineswar with an ecstatic devotional practice quite unlike Brahmo rationalism, attracted a circle that included Narendranath Datta, who as Vivekananda addressed the Chicago Parliament of Religions in 1893 and founded the Ramakrishna Mission. The vocabulary in which Hinduism is now presented internationally largely comes out of that Bengali generation.
The region was then partitioned in 1947 along religious lines, with the Muslim-majority east going to Pakistan, and millions moved. In 1971 the same territory divided again, this time on language and political grounds rather than religious ones, when East Pakistan became Bangladesh after a war in which enormous numbers were killed and Hindu villages were specifically targeted.
Bengal therefore carries two partitions of different kinds, and its religious history since 1947 is inseparable from both.