Before Donald H. Rumsfeld entered his second tenure as Secretary of Defense in 2001, the selection of senior U.S. military officers for top-ranking positions within the Department of Defense (DoD) was largely decided within the uniformed services, and the Secretary of Defense did not typically challenge the recommendations. However, to support his goal of transforming the defense establishment, Rumsfeld decided to become personally involved in the selection process. Rumsfeld's changes resulted in a process that featured long-term succession planning, identified qualifications for senior positions, built a slate of highly qualified officers, and sought to arrive at a series of "best fit" decisions for the top military positions. The process also focused on planning for the future by identifying highly capable leaders and associating them with a series of assignments that would prepare them for the top military positions. When Rumsfeld left DoD in 2006, parts of the process he developed were retained, and others were changed significantly or discarded. The process has continued to evolve, at times rekindling some of the efforts Rumsfeld initiated but reshaping them to suit the leadership style of current DoD officials. The authors review senior leader selection and succession planning in general, describe the process developed by Rumsfeld, and investigate how the process evolved after Rumsfeld left office. In conclusion, they identify key system attributes that future DoD officials should consider as they contemplate how senior officer selection and assignments will be managed.