Query: In what month and year was a blanket nationalization of foreign oil production proclaimed?
Context: Increasing state control over the oil sector, the RCC began a program of nationalization, starting with the expropriation of British Petroleum's share of the British Petroleum-N.B. Hunt Sahir Field in December 1971. In September 1973, it was announced that all foreign oil producers active in Libya were to be nationalized. For Gaddafi, this was an important step towards socialism.