Change is hard, especially in a large organization. Numerous studies have shown that employees tend instinctively to oppose change initiatives because they disrupt established power structures and ways of getting things done. However, some leaders do succeed—often spectacularly—at transforming their workplaces. What makes them able to exert this sort of influence when the vast majority can’t? So many organizations are contemplating turnarounds, restructurings, and strategic shifts these days that it’s essential to understand what successful change agents do differently. We set out to gain that insight by focusing on organizations in which size, complexity, and tradition make it exceptionally difficult to achieve reform.