Fortress Investment Group began in 1998 as a pure private equity firm and diversified in 2002, when founders Wesley Edens, Robert Kauffman and Randal Nardone hired Goldman alumni Peter Briger and Michael Novogratz to launch the firm's credit business and to manage macro hedge funds (known as the liquid markets business), respectively. The firm's fourth business, traditional long-only fixed-income manager Logan Circle Partners, was acquired in 2010, creating what the principals call "a business for all seasons." In its early days the firm's diversification strategy, in which different businesses performed better during different times in the economic cycle, worked well…