Bush's top goals were to 'strengthen the nation's space leadership and ensure that space capabilities are available in time to further U.S. national security, homeland security, and foreign policy objectives" and to "enable unhindered U.S. operations in and through space to defend our interest there." The Bush policy called on the Secretary of Defense to provide "space capabilities" to support missile-warning systems as well as "multi-layered and integrated defense. Sections of the 1996 Clinton policy and the Bush revision have similarities, and the general principles of U.S. space policy have changed very little since they first appeared in the Carter Administration's PD/NSC-37 of 1978. The NSC and the Department of Defense emphasized that continuity with previous policies. But some see a significant divergence apparent in the first two goals of each document.