Pierre Trudeau resigned as Prime Minister in 1984 after taking a "long walk in the snow" to consider his future. Brian Mulroney became Canada's new Prime Minister and sought closer ties with the United States, unlike Trudeau who tried to separate Canada from US interests. When the US announced its Strategic Defense Initiative, nicknamed "Star Wars", it created tension as Canada's role in NORAD was unclear and anti-nuclear groups protested potential Canadian involvement, worried it could provoke an arms race.