The 2002 National Security Strategy (NSS) called for a shift in objectives and methods in dealing with threats to national security from an emphasis on law enforcement to prevention based in part on the use of force. The NSS proposed that, in addition to continued reliance on diplomacy, economic sanctions, and other methods short of the use of force, the U.S. should resort to force in order to prevent grave dangers where necessary, in some cases even when the threat they pose is not imminent, and despite the absence of Security Council approval. These positions raise important and unsettled issues, which the sponsoring organizations propose to consider at a meeting on Preventive Force, to be held from May 25th to May 27th, 2005, at the headquarters of the Hewlett Foundation in Menlo Park. It is being planned and organized by the Hoover Institution, in cooperation with the Hewlett Foundation and the Stanford Institute for International Studies. The meeting on Preventive Force will bring together a small group of practitioners, scholars, and officials experienced in the relevant fields of international security affairs to discuss the following issues among others: the need to consider using preventive force; the nature of preventive (as opposed to preemptive) force; the dangers of relying on preventive force as part of a national security strategy; the standards by which resort to preventive force should be governed, if its use is ever appropriate; and the principles and measures that might if adopted reduce the need to resort to preventive force. In addition to panels and speakers on these subjects, the meeting will include a televised session for the PBS program "Uncommon Knowledge," at which some of the participants will offer perspectives on the utility and wisdom of relying on preventive force as an avowed element of U.S. national security, and on the role of the Security Council in controlling such decisions. We will be joined by scholars from the Brookings Institution and members of the Princeton Project on National Security, sponsored by Princeton's Woodrow Wilson School of Public and International Affairs. We appreciate their help in preparing a program for the initial meetings. We will also have the participation of Stanford's Center for International Security and Cooperation.