The decision to split Bengal came in July and by October 16, 1905, Bengal had been divided into Piston Bengal and Assam (with a population of 31 million) and the rest of Bengal (with a population of the 4 million of who 18 million were Bengalis, and 36 million Biharis and Oriyas). The decision had come after Lord Curzon claimed that Bengal was too large to be governed effectively