Following Labour's victory at the 1964 election, Wilson appointed Callaghan as Chancellor of the Exchequer; this appointment coincided with a turbulent period for the British economy, during which Callaghan had to tackle both a chronic balance of payments deficit and various speculative attacks on the pound sterling, with its exchange rate to other currencies being fixed by the Bretton Woods system. On 18 November 1967, having initially denied that it would do so, the Government devalued the pound sterling. In the wake of the decision, Wilson moved Callaghan to the role of home secretary. During this time, Callaghan was responsible for overseeing the operations of the British Army to support the police in Northern Ireland, following a request from the Northern Ireland government. Callaghan remained in the Shadow Cabinet during Labour's period in Opposition from 1970 to 1974; upon Labour's victory at the 1974 election, Wilson appointed Callaghan as foreign secretary. Callaghan was responsible for renegotiating the terms of Britain's membership of the European Communities (EC), and strongly supported the "Yes" vote campaign in the 1975 referendum, which confirmed the UK's membership of the EC.