The development and procurement of major weapons programs in the United States is a complex and often drawn-out process complicated by political considerations and often sharp disagreements over requirements and the merits of systems. Secretaries of Defense since Robert McNamara have sought to impose discipline on the process, with varying degrees of success. Conflicts between a Military Service and the civilian leadership are inevitable. A Service wants to develop the most advanced system to address its perceived need, whereas the Secretary of Defense must balance competing requirements across the Department of Defense. The military and the civilian leadership may also have different strategic perspectives that feed this conflict. Through the detailed analysis of three case studies-the Nuclear Surface Navy in the 1960s, the B-1 Bomber in the 1970s, and the Crusader Artillery System in the 2000s–the author explores some of the common themes and sources of friction that arise in civil-military relations concerning major weapons programs. He concludes with some thoughts on how the Secretary of Defense can anticipate and reduce these sources of friction, while retaining an environment that supports healthy debate.