The debate over credit for Libya's shift away from “rogue state” policies, most especially by settling the Pan Am 103 Lockerbie terrorism case and abandoning its weapons of mass destruction (WMD) programs, is lively politically and challenging analytically. It has important implications for theories of force and diplomacy, particularly coercive diplomacy, and policy debates including such cases as Iran and North Korea. U.S. coercive diplomacy against Libya can be divided into three phases: the Reagan strategy of unilateral sanctions and military force, which largely failed; the mixed results from the more multilateral strategy of the George H.W. Bush and Bill Clinton administrations; and the substantial success achieved through the secret direct negotiations initiated along with Britain in the latter Clinton years and furthered under George W. Bush, which culminated in Libya closing down its WMD programs. These differences in success and failure are principally explained by (1) the extent of “balance” in the coercer state's strategy combining credible force and deft diplomacy consistent with three criteria—proportionality, reciprocity, and coercive credibility—taking into account international and domestic constraints; and (2) target state vulnerability as shaped by its domestic politics and economy, particularly whether domestic elites play a “circuit breaker” or “transmission belt” role in blocking or carrying forward external coercive pressure.