Many diplomatic and military practitioners as well as theorists have argued that successful execution of a military operation depends on how well specific actions are matched to strategic intent. It has been argued that the imposition of any no-fly zone, a particular form of military operation, should begin with a clear articulation of strategic-level goals. For any given situation, such "grand strategy" might include, in this order: a clear statement of the U.S. national interests at stake; a vision of the political endstate—the strategic-level outcomes—that would help secure those interests; a clear articulation of the major steps—the ways and means—including diplomatic, political, and economic as well as military, to be employed in order to accomplish the desired endstate, including the objectives each is designed to achieve; and a consideration of the nature and extent of political "risk" in the proposed approach—including the potential impact of proposed actions on the civilian population in the targeted country, on the region, on broader international partnerships, and on perceptions of the U.S. government both at home and abroad. The military strategy designed to support the grand strategy, it has been suggested, might be based on these considerations: the operational-level military objectives that need to be achieved, to support the overall grand strategy, and the extent to which a no-fly zone—as one set of ways and means—helps achieve those objectives. Recent operational experiences suggest that the establishment of a no-fly zone, in itself, is unlikely to achieve the full set of military objectives, such as protecting a civilian population, let alone the grand strategic objectives, such as restoring or removing a regime. In key recent "no-fly zone" cases, observers suggest that the strategic planning process may have emphasized "mid-range" operational-level concerns at the expense of higher-level strategic concerns. In Operation Odyssey Dawn, Operation Northern Watch, Operation Southern Watch, and Operation Deny Flight, the match between the application of one military approach—the no-fly zone—and broad strategic goals, many assess was at best incomplete. Operation Odyssey Dawn, a coalition operation conducted during early 2011 over Libya, was put in place to enforce United Nations Security Council Resolution 1973, which authorized force to protect civilians in Libya. Facing a popular uprising, the Libyan government under Muammar al Qadhafi had responded with attacks against population centers with armor, artillery, and air strikes. Going beyond a pure no-fly zone, Operation Odyssey Dawn prevented Libyan air forces from operating against civilians, while including attacks against pro-Qadhafi ground forces that were perceived to be threatening civilian populations. Although Odyssey Dawn included establishment and enforcement of a no-fly zone, it also included strike operations against Libyan government forces perceived to be attacking civilian populations, and the command and control and logistics networks supporting those forces. More information on Operation Odyssey Dawn can be found in CRS Report R41725, Operation Odyssey Dawn (Libya): Background and Issues for Congress . Operation Northern Watch (ONW), a combined operation involving U.S., UK, and French forces conducted from 1991 to 2003, was designed to enforce a no-fly zone in northern Iraq, north of the 36 th parallel, in order to prevent Iraqi repression of the concentrated ethnic Kurdish population living in that part of the country. The Iraqi government led by Saddam Hussein had already made use of Iraqi airspace to attack Iraqi Kurds in Halabja with chemical weapons in 1988. Acts of repression after the conclusion of the early 1991 Gulf War had displaced many Iraqi Kurds. The immediate aim of ONW was to protect the population from further attacks by the Iraqi military, and it is generally considered that ONW largely achieved this operational objective. At the strategic level, ONW took place against the backdrop of international pressure on the Iraqi government to comply with an international weapons inspection regime, in accordance with U.N. Security Council resolutions. Missing from ONW, in any explicit way, was a vision of political endstate, or a stated theory of the case linking the no-fly zone to that endstate. Similarly, Operation Southern Watch (OSW), a U.S.-led coalition operation, was designed to protect the Shi'a Arab population of southern Iraq from repression and retaliation by Iraqi government forces in the wake of the Gulf War. The Iraqi government had made use of its own airspace to conduct bombing and strafing runs targeting Shiite citizens. In terms of immediate operational objectives, OSW is generally considered not to have prevented Iraqi government repression of its southern population. At the strategic level, while some U.S. officials had reportedly considered, at one time, that in the wake of the Gulf War southern Iraqi Shiites might rise up to demand the ouster of Saddam's regime, OSW does not appear to have been guided by any explicit vision of political endstate. Operation Deny Flight (ODF) was a NATO operation that banned all flights—with some exceptions—in the airspace of Bosnia and Herzegovina from April 1993 to December 1995. The military objectives included denying the use of that airspace to Bosnian Serb aircraft, in order to protect the population and facilitate the delivery of humanitarian assistance. Observers have debated the ODF's degree of success in this regard—while humanitarian work by international relief organizations was protected to some extent, Bosnian Serb aircraft periodically defied the flight ban to stage attacks, while on the ground, for example, Bosnian Serb forces overran the U.N. safe haven in Srebrenica, in 1995, killing thousands. At the strategic level, ODF may have come closer than the no-fly zone operations in Iraq to linkage with strategic objectives. In the preamble of the 1992 U.N. Security Council resolution authorizing ODF's precursor, a no-fly zone banning military aircraft, the Council "consider[ed] that the establishment of a ban on military flights in the airspace of Bosnia and Herzegovina constitutes an essential element for the safety of the delivery of humanitarian assistance and a decisive step for the cessation of hostilities in Bosnia and Herzegovina." Some experts believe that the Bosnian no-fly zone contributed directly to the ultimate cessation of hostilities; others suggest that its contribution is difficult to separate from the roles of close air support and the ground presence of U.N. troops. There is little evidence to suggest that a clear and specific vision of the political endstate that might follow a cessation of hostilities informed the creation of the no-fly zone. Practitioners and observers have debated what constitutes international "authorization" for the establishment of a no-fly zone. Given the paucity of relevant precedents, and the dissimilarities among them, there may not exist a single, clear, agreed model. Authorization may be not only a question of approval or disapproval. It may also include parameters for the execution of the mission, and conditions under which the authorization for the no-fly zone operation will be considered discontinued. It may not be necessary to achieve all of the broad objectives of grand strategy before discontinuing the no-fly zone—the no-fly zone operation may be designed to catalyze overall progress toward those objectives. In turn, the concept of authorization is typically considered to be linked to the ideas of both "legality" and "legitimacy"—the three concepts overlap but are all distinct. The precise meaning of each of the terms is still debated. The legality of a no-fly zone operation may depend, at a minimum, on both authorization for the operation and the extent to which the manner of execution of the operation comports with relevant international law. The Charter of the United Nations, in Article 2(4), prohibits the "threat or use of force against the territorial integrity or political independence" of a member state under most circumstances, and many practitioners and observers have wondered whether the establishment of a no-fly zone would constitute a violation of this prohibition. In practice, the answer may depend on the circumstances—and in some cases there may be no general agreement about what the empirical circumstances indicate. There are at least three sets of circumstances that do—or may—constitute exceptions to this prohibition. The first basis for an exception is U.N. Security Council authorization based on the powers granted to the Council by Chapter VII of the U.N. Charter to respond to threats to international peace and security. That Chapter authorizes the Security Council to "determine the existence of any threat to the peace, breach of the peace, or act of aggression" and to "make recommendations, or decide what measures shall be taken ... to maintain or restore international peace and security." Express authorization from the Security Council provides the clearest legal basis for imposing a no-fly zone. The second basis for an exception is self-defense. Article 51 of the Charter explicitly recognizes the right of self-defense as an exception to the prohibition. The Article states, "Nothing in the present Charter shall impair the inherent right of individual or collective self-defense if an armed attack occurs against a Member of the United Nations." Some theorists and practitioners consider that there also exists a customary doctrine of self-defense outside of the U.N. Charter that permits military action to prevent a grave threat to regional peace and stability, even if that threat seems to be contained within the borders of a state. According to this view, armed intervention within a state is not a prohibited "use of force" so long as it is not aimed at taking a state's territory or subjecting its people to political control (a narrow reading of "use of force against the territorial integrity or political independence of any State"), and is not otherwise inconsistent with the intent of the U.N. Charter.