By the 1960s, the SNP was starting to become defined ideologically, with a social democratic tradition emerging as the party grew in urban, industrial Scotland, and its membership experienced an influx of social democrats from the Labour Party, the trade unions and the Campaign for Nuclear Disarmament. The emergence of Billy Wolfe as a leading figure in the SNP also contributed to the leftwards shift. By this period, the Labour Party were also the dominant party in Scotland, in terms of electoral support and representation. Targeting Labour through emphasising left-of-centre policies and values was therefore electorally logical for the SNP, as well as tying in with the ideological preferences of many new party members. In 1961, the SNP conference expressed the party's opposition to the siting of the US Polaris submarine base at the Holy Loch. This policy was followed in 1963 by a motion opposed to nuclear weapons: a policy that has remained in place ever since. The 1964 policy document, SNP & You, contained a clear centre-left policy platform, including commitments to full employment, government intervention in fuel, power and transport, a state bank to guide economic development, encouragement of cooperatives and credit unions, extensive building of council houses (social housing) by central and local government, pensions adjusted to cost of living, a minimum wage and an improved national health service.