Decision making for U.S. national security is not a static process. Presidents adjust their decision-making structures from time to time when they perceive that the standard interagency procedures no longer serve their political purposes. This article identifies a distinct pattern in the evolution of national security decision structures over time by examining Carter, Reagan, and G. H. W. Bush decision making on nuclear strategy and arms control. Similarities in each administration's structural changes stem from institutional and political pressures. The differences in the shape of those changes have their origin in the idiosyncratic leadership styles of each president.