Montreal-based CGI Group has agreed to purchase information technology business Stanley in order to expand its reach into the US defense contracting market. Arlington, Virginia-based Stanley provides technology services to military, intelligence and government agencies. The acquisition will make CGI's federal unit a government IT provider with more than $1 billion in annual revenue. Montreal-based CGI created its federal arm, which is headquartered in Fairfax, when it purchased American Management Systems in 2004.