This study examines U.S. policy toward missile defense (MD) focusing both on the international opportunities opened up for the U.S. after the Cold War and on the variation of domestic policy consensus at the governmental level that influenced the actual decision making regarding the deployment of the current MD system. Based on the insights of offensive realism, this study argues that the U.S.'s pursuit of MD is related to U.S. strategic calculations motivated by systemic incentives and opportunities. This study also addresses how domestic policy consensus played an important role in determining the timing and nature of the decision toward the deployment of the current MD. By comparing the U.S.'s different policy paths under the Clinton and the Bush administrations, and analyzing U.S. experiences with MD during the Cold War, this study concludes that the U.S. is about to deploy an MD system because it has power and resources to pursue strategic advantages, not because a new threat enforces the deployment of the system on it. Facing no peer competitor who can directly challenge U.S. exploitation of international opportunities, the U.S. began the active deployment of the system only after the effective veto dissolved by way of the Republican full control over both executive and legislative branches. In other words, international opportunities and domestic policy consensus have been the main determining factors shaping the policy outcomes regarding the current MD. While international opportunities gave the U.S. a strong incentive to pursue MD as an additional power component, policy consensus at the governmental level enabled the U.S. to mobilize domestic resources for the power pursuit.