Recent years have witnessed a growing interest, in Congress, in the executive branch, and in the broader policy community, in re-examining how well the U.S. government conducts the business of national security—from decision-making, to strategy-making, to budgeting, to planning and execution, to accountability and oversight. That interest reflects concerns with effectiveness—how well the U.S. government accomplishes the mission—and with efficiency—how well the U.S. government stewards scarce resources—in the national security arena. Within the context of these debates, a number of practitioners and observers have called for the adoption of "unified"—or "consolidated" or "integrated"—approaches to national security budgeting. The primary concern of this unified national security budgeting school, loosely defined, is not to improve U.S. budgeting practices per se , but rather to use budgetary mechanisms to drive changes in the priorities and practice of national security. Members of the school broadly share the view that some U.S. national security concerns, such as counter-terrorism, or stabilization and reconstruction, are inherently cross-cutting: that is, they require the participation of multiple agencies, and their associated responsibilities could conceivably be divided up any number of ways among various agencies. In turn, members of the school argue that the current system allows little space for holistic consideration of such cross-cutting national security issues, and they propose an array of budgetary tools designed to promote cross-fertilization. They suggest that for such cross-cutting issues, more "unified" budgeting approaches could facilitate the identification of overlaps and gaps among agencies' efforts; enable more deliberate assignment of roles and responsibilities; catalyze closer collaboration; and provide greater transparency to help support congressional oversight. Such changes, they add, could improve effectiveness and save money. The school itself is far from unified—there is no single model for "unified national security budgeting." Various proponents have put forward quite different proposed remedies and are—apparently—aiming to solve quite different underlying problems. The fact that the debate itself is not cohesive has no logical bearing on the value of the various associated proposals, but it suggests a need to define terms, as a starting point. For Congress, constitutionally mandated to control the power of the purse, fundamental issues at stake include both oversight of the effectiveness and efficiency of U.S. government national security activities, and the integrity of the overall federal system of budgeting. Of particular interest may be the extent to which, if any, efforts to optimize the overall system, and efforts to optimize its national security "sub-system," constitute competing imperatives. This report describes and characterizes the unified national security budgeting school's broadly shared critique of the current system; describes and analyzes various proposed unified national security budgeting approaches; and offers a succinct list of considerations for Members and staff of Congress who may be interested in this issue. The U.S. government system of budgeting for national security activities is part of a much larger, highly complex system of federal budget development—based on the constitutional distribution of roles and responsibilities between Congress and the President, on statute, and on a wide array of established practices by key stakeholders. The system necessarily covers the full panoply of U.S. government responsibilities and activities, and therefore by definition—de facto if not explicitly—adjudicates among all competing concerns. In a sense, the federal budget system not only reflects the distribution of power among branches, but also refines and institutionalizes that power balance. So the stakes associated with any possible revision of the federal budget system are quite high. The current, extremely complex federal budgeting system includes at least three major processes directly germane to the consideration of national security. In the executive branch, the Office of Management and Budget (OMB), part of the Executive Office of the President (EOP), is responsible for administering budget development and execution. OMB typically assigns each federal Department and agency an informal topline—a total funding limit—early in the process. OMB may also provide additional funding level guidance for some specific activities. Agencies then typically work within their respective toplines, which can be negotiable, to craft their budget requests. The appropriate Resource Management Offices (RMO) within OMB consider the draft requests and work with agencies to refine them. OMB leadership considers the findings—a process in which National Security Staff (NSS) members, for national security-related matters, may participate. OMB "passes back" its decisions to agencies, revisions are made, any agency appeals are adjudicated, final EOP decisions are taken, and the results are put forward to Congress as the President's budget request. In Congress, appropriations committees allocate shares of the discretionary budget to their subcommittees, each of which has specified oversight responsibilities. Each subcommittee's remit corresponds to some broad mission area—such as "defense" or "homeland security." But those remits do not fully align with Departments and agencies—subcommittees may be responsible for some activities at multiple agencies, and agencies may answer to more than one subcommittee. Meanwhile, as an organizing construct, the entire federal government uses a hierarchy of categories—budget "functions" and "sub-functions," based on the purpose the funding is intended to serve—to organize compilation and consideration of budget requests. These functions do not fully align with Departments and agencies, nor do they correspond directly to appropriations subcommittees—for example, there is no single budget function for "homeland security," which is both an agency and a subcommittee title. According to a number of practitioners, budget function categories do not fully reflect the way that budget requests are developed or considered in either participating branch of government. The current system does not budget for national security in an explicit and bounded way. There is no legal definition stating how "national security" maps onto any of the sets of boundaries used in the current budget process—including executive branch agencies, appropriations subcommittees, or budget functions. It is worth noting that bounding "national security" for the purposes of budgeting would require more than organizational or administrative fixes; it would also require significant conceptual efforts to define the boundaries of the category. The broader policy community has no single, shared understanding of the arenas and activities that contribute to national security. In practice, the debates about boundaries tend to be shaped by real-world developments. For example, in the wake of the terrorist acts of September 11, 2001, many practitioners and observers urged closer integration between homeland security and traditional national security efforts. The Obama Administration, at the start of its first term, declared the two "indistinguishable" and institutionalized the concept organizationally with a merger of the previously separate National and Homeland Security Councils. Yet on one hand, it is not obvious that all national and homeland security concerns should be combined, for all purposes. And on the other hand, contributions to U.S. national security might be defined more broadly still—to include energy, the environment, and the economy, for example. In principle, incorporation of some activities that are not traditionally included under a national security umbrella might give them additional prominence and might even boost their chances of getting funded. Even more ambitiously, broadening the scope of "national security" in the budgeting process might encourage practitioners to think more creatively about how various instruments of national power contribute to U.S. national security, and to use resourcing decisions to re-balance the weight of those contributions. Yet inclusion of broader activities in the national security mix could conceivably have the opposite effect by sharpening the zero-sum contest for resources between traditional and less-traditional national security tools. Unified national security budget advocates typically characterize the current system in at least two important ways. First, they rightly point out that the current system does not treat "national security" in a distinct, bounded way. Second, they tend to argue that the various national security-related components of the budget are developed in striking isolation from one another. They suggest that the executive branch process would do well to undertake more ambitious cross-cutting consideration of national security issues; and they add that in practice it is better at ensuring the internal consistency of each agency's budget request than at reconciling the requests of various agencies. They suggest that appropriations committees would do well to adjudicate more actively how cross-cutting national security priorities are met by adjusting the mix of activities undertaken, or the division of labor among agencies, or both. But they argue that in practice, subcommittees tend to guard against perceived incursions into their respective jurisdictions, and full committee-level adjudication is relatively rare. Skeptics might raise concerns about any of several broadly shared facets of UNSB community thought. First, they might point to the relatively limited attention UNSB advocates tend to give to the integrity of the federal government budgeting system—to the damage that might be done to the overall system including, not least, congressional oversight, by changes to any of its basic modalities. Second, some might suggest that the UNSB community typically fails to consider what additional room there might be for holistic consideration of cross-cutting issues within the formal bounds of the current system through fuller utilization of existing tools. Third, skeptics might observe that "national security" is but one subset of overall U.S. concerns, and that optimizing for national security might well mean sub-optimizing in other arenas and at the level of U.S. government responsibilities. Finally, some suggest that unified budgeting advocates may be particularly eager to label national security activities as "cross-cutting," viewing holistic consideration as an additive good without associating any opportunity costs with the forfeiture of single-agency responsibility. In principle, single agency-based approaches may sometimes offer greater efficiency and greater effectiveness. Further, unified budgeting advocates may tend to believe that an activity either is cross-cutting or it is not.