Sub-divisional Officer an official in charge of a field level unit of administration called 'sub-division' existed until 1982 when the government took a decision to upgrade all the existing sub-divisions into 'districts'. The creation of the sub-division comprising a group of thanas in effect dates back to 1859. The main purpose was to decentralize district administration and to bring the field administration closer to the rural people, and to ensure in particular the expeditious disposal of criminal cases. This unit was headed by the sub-divisional magistrate (SDM) but officially and more popularly known as sub-divisional officer (SDO). As a unit 'subdivision' seemed to have been peculiar to Bengal before partition, and to East Bengal after the partition in 1947, for its corresponding units in other provinces in the subcontinent were 'tehsils' and/or 'talukas'.

Although in the early years an SDM (or SDO), aided by a number of other magistrates, was primarily responsible for prompt disposal of criminal cases, over time he seemed to have surrendered his image and authority as an officer as such. For all practical purposes an SDO appeared to have been exercising, subject to the general control and supervision of the deputy commissioner, almost all functions that the latter used to exercise in the district. After 1961, SDO became the ex-officio chairman of the thana council, a thana-based local government body, under the basic democracies system introduced in Pakistan in 1959. [AMM Shawkat Ali]