Scholars studying the processes that lead to significant alterations in public policies have identified two major sources of change: policy-oriented conflict and policy-oriented learning. Many investigations of specific cases of consequential policy change also suggest that “shocks” from outside the policy subsystem, (that is, the specific political arena where a policy issue is formulated and implemented) are often necessary for significant policy change to occur. Rather than being competing explanations of policy change, this paper argues that external shocks, conflict, and learning often interact to generate windows of opportunity which enable policies to be significantly altered. These perspectives on policy change are then qualitatively applied to recent changes in U.S. national security policy which have allowed formerly secret spy satellite technology to be used in commercial data gathering systems. The final part discusses the implications of this research for the theory of policy change and for U.S. national security policy.