The 1995 Dayton peace agreement ended a 3 1/2-year war that pitted Bosnia's Muslim, Croat, and Serb communities against one another. NATO first deployed an Implementation Force (IFOR) of nearly 60,000 troops to Bosnia to enforce compliance with the military aspects of the Dayton accords. Although IFOR successfully carried out the military tasks outlined in the Dayton agreement, the continued need for an external military presence to provide a secure environment in Bosnia led NATO to replace IFOR with a smaller Stabilization Force (SFOR, initially with about 32,000 troops) in December 1996. NATO extended SFOR a second time in June 1998, this time without a specified end-date. Instead, NATO outlined a number of benchmarks to measure progress toward a self-sustaining peace in Bosnia. Periodic mission reviews by NATO of SFOR operations assessed an increasingly stable security situation and prompted gradual reductions in SFOR's force strength over time. The U.N. Security Council authorized NATO's original IFOR mission in December 1995, the follow-on SFOR mission one year later, and subsequently renewed its authorization for SFOR's operations on an annual basis. The United States initially contributed close to 20,000 troops to IFOR, or about one-third of the total force. In 1995, President Clinton justified the U.S. contribution as an appropriate response to the suffering and instability caused by the Bosnian war and as a demonstration of U.S. leadership in NATO, although he pledged at the time that the commitment would not exceed one year. The Bush Administration frequently invoked the "in together, out together" policy with the European allies on maintaining transatlantic unity on Balkan peacekeeping operations. As the smaller SFOR drew down over the years, so did the U.S. contingent, and its share averaged about 15% of the total force in the final years (for example, the U.S. contribution was about 1,000 out of a total of 7,000-8,000 troops in SFOR in late 2004). Throughout SFOR's existence, the United States retained command over the NATO force in Bosnia; NATO's residual headquarters presence also remains under U.S. command. About 1,500 U.S. troops currently serve in the NATO peacekeeping force in nearby Kosovo. EU heads of state expressed their willingness and readiness to lead a military operation to follow SFOR as early as 2002. EU officials viewed the initiative to lead a follow-on peacekeeping force in Bosnia as an outgrowth of the EU's European Security and Defense Policy (ESDP), as well as a logical extension of the EU's growing involvement in the western Balkans. Bosnia is in negotiations with the EU on a Stabilization and Association Agreement and aspires to eventual EU membership. The EU also has experience in fielding a police training and advisory mission in Bosnia in the ESDP framework--the EU Police Mission in Bosnia currently comprises just over 150 international police personnel, and its mandate was extended and amended in late 2007 through 2009. The Dayton-mandated Office of the High Representative is "double-hatted" as the EU's Special Representative in Bosnia and is expected eventually to evolve into an EU-only office. By assuming peacekeeping duties in Bosnia, EU members aimed to further develop ESDP on an operational level, as well as complement the broader EU integration strategy for Bosnia. By the December 2003 NATO ministerial meetings, some apparent differences between NATO and the EU had been worked out, and NATO members reached consensus on the concept, if not yet the details, of a follow-on EU military mission in Bosnia. A fundamental principle agreed to early on was that any EU military mission in Bosnia should fall within the so-called Berlin Plus framework. Berlin Plus refers to arrangements finalized in late 2002-early 2003 on institutional and operational links between NATO and the EU that grant the EU access to NATO planning and assets for operations in which NATO is not engaged. The first test case for Berlin Plus occurred in early 2003 with the EU's takeover of the small NATO mission in Macedonia. NATO's Allied Harmony mission in Macedonia was concluded in March 2003 and replaced by the EU's Operation Concordia , a small and limited mission of 350 troops that ended in December 2003. Conceptual details of the transition evolved as NATO and EU planners worked to develop plans for mid-2004 summit meetings. Early agreed concepts included formally concluding SFOR and putting in place a new and distinct EU mission in a seamless transition. The EU mission was to emphasize broader reform objectives in Bosnia, including closer association with the EU. An issue of initially greater contention centered on the form and function of the residual NATO "headquarters presence," which NATO officials said would assist with defense reform functions, such as training and inter-operability exercises in conjunction with Bosnia's expected future membership in NATO's Partnership for Peace (PFP), as well as intelligence collection, counterterrorism, and apprehension of persons indicted for war crimes. This proposed multifaceted set of tasks for the residual NATO presence suggested to some a more robust operational capability than just an advisory or support presence. Some European officials reportedly resisted plans that could have led the NATO presence to parallel functions of the EU force and emphasized the need for the EU to maintain full operational control of, and autonomous decision-making authority over, the military mission. In the final arrangement, EUFOR took over the primary military stabilization role, while the NATO headquarters presence was to focus primarily on defense reform. However, both share some operational tasks. Many observers maintain that the unresolved war criminals issue clouded the transition and the legacy of SFOR, especially with respect to former Bosnian Serb leader and wanted war crimes suspect Radovan Karadzic. Despite numerous campaigns by SFOR, the OHR, and local Bosnian agencies to increase pressure on Karadzic, including detaining his close associates and sanctioning or dismissing his alleged supporters, Karadzic (as well as former Bosnian Serb General Ratko Mladic) continues to elude capture. Prior to the December 2004 handover, the United States appeared to send somewhat contradictory signals at times on the desired level of U.S. engagement in the Balkans. On the one hand, some U.S. officials, especially in the military, expressed an interest in concluding the U.S. military role in the Balkans in view of greater or more pressing U.S. priorities in Iraq, Afghanistan, and elsewhere. For them, handing over operational security matters to the EU in Bosnia represented another opportunity, in a relatively secure environment in Europe, for global security burden-sharing. The larger EU role is also seen to be consistent with U.S. goals for the western Balkan region that include its eventual full integration into the EU. On the other hand, some U.S. officials may have been initially wary of French and other European long-term aspirations to build up European military structures separate from NATO, and concerned that successful EU missions such as the one in Bosnia could work to diminish NATO's primacy--and possibly U.S. influence--on European security matters. Another perspective has been that an ongoing U.S. military presence has served as a key stabilizing factor in Bosnia and should not be eliminated entirely. The transition from NATO to the EU force incurred no discernible political impact in Bosnia. During the EUFOR planning stage, Bosnian government officials accepted the concept of a European follow-on force, although they emphasized the need for a continued NATO and U.S. presence. Bosnian officials often cite the critical role of U.S. leadership in eventually bringing an end to the Bosnian war in 1995, especially in the wake of failed U.N. peacekeeping missions (comprised largely of European forces) during the Bosnian war. After the handover, about 200 U.S. forces remained in Bosnia as part of the NATO headquarters presence in Camp Butmir in Sarajevo and at the U.S. Eagle Base in Tuzla (on the basis of a bilateral military agreement). The residual U.S. presence at both bases was involved in providing intelligence support, engaging in efforts to detain war crimes suspects, and working to deny safe havens for Islamist extremists and their supporters in Bosnia. In 2006, the United States announced the withdrawal by the end of the year of its forces at Eagle Base; a small number of U.S. intelligence officers continue to serve with the NATO Headquarters presence, which remains under U.S. command. The December 2004 handover ceremony marked an important milestone both for Bosnia's future and for the EU's aspirations to assume greater security responsibilities. EUFOR is seen as an important precedent for future potential mission handovers from NATO to the EU, for example possibly in Kosovo (although peacekeeping functions there remain with NATO). EU members have sustained their support for contributing to a safe and secure environment in Bosnia, even while the emphasis has shifted from a large military presence to greater political engagement. EUFOR has conducted several exercises and operations aimed at collecting illegal weapons, improving coordination with NATO, disrupting organized criminal activity, and supporting de-mining programs. EUFOR has worked closely with Bosnian law enforcement agencies on combating organized crime, including conducting joint anti-crime operations and arrests. Small units of Liaison and Observation Teams (LOT) have been stationed to increase EUFOR visibility in local communities. Both EUFOR and the NATO presence remain engaged in the pursuit of war crimes fugitives and in pressuring their support networks, in close cooperation with Bosnian authorities and the international war crimes tribunal. Prior to its transition in 2007, EUFOR comprised some 6,200 troops from twenty-four EU member states and ten other countries, with Germany, Italy, France, and the United Kingdom leading troop contributions. The force was divided into three multinational task forces under British, Spanish, and Finnish regional command, with EUFOR headquarters in Sarajevo. Over a six-month period in 2007, EUFOR was downsized and restructured. Its current force of about 2,500 troops from 22 EU and 6 non-EU states serve in a single multinational manouevre battalion based in Sarajevo and in small Liaison and Observation Teams (LOTs) throughout Bosnia. Germany and Italy lead troop contributions; the U.K. withdrew most of its contingent in 2007. EUFOR's current force commander is Gen. Ignacio Martin Villalain of Spain. The EU's Political and Security Committee continues to provide political guidance and strategic direction. EU officials insist that EUFOR remains an effective military force, capable of carrying out its enforcement mandate throughout Bosnia and of quickly adding reinforcements if necessary. Meanwhile, the ongoing NATO presence in Bosnia serves to reinforce the transatlantic dimension and Bosnia's aspirations to join NATO; Bosnia's admittance into NATO's Partnership for Peace program in late 2006 marked the start of expanded engagement with NATO. Outside of Bosnia but within the region, tensions may increase in conjunction with the anticipated resolution of Kosovo's disputed status in 2008. On April 26, 2004, EU members endorsed a "General Concept" for an EU-led mission in Bosnia, including a military component of about 7,000 troops. The concept established the broad strategy for the EU's engagement in Bosnia. It called for the EU military operation to fulfill the military tasks of the Dayton peace agreement, have a mandate authorized by the U.N. Security Council under Chapter VII of the U.N. Charter, and come under the political authority of the EU Council's Political and Security Committee (PSC). At its June 28-29 Istanbul summit, NATO nations confirmed the decision to conclude SFOR by the end of 2004 and agreed that NATO's residual military presence would have the "principal task" of providing advice on defense reforms and would also "undertake certain operational supporting tasks, such as counter-terrorism...; supporting the ICTY...with regard to the detention of persons indicted for war crimes; and intelligence sharing with the EU." On July 9, the U.N. Security Council unanimously passed Resolution 1551 which welcomed "the EU's intention to launch an EU mission to Bosnia and Herzegovina, including a military component, from December 2004." On July 12, EU members adopted a "Joint Action" on the EU military operation in Bosnia, named Althea . It designated the EU Operation Commander and EU Force Commander and reaffirmed the EU's comprehensive approach toward Bosnia and support for EU integration. On October 11, the EU Council approved the Operational Plan for the EUFOR Operation Althea . The U.N. Security Council passed Resolution 1575 on November 22. Acting under Chapter VII of the U.N. Charter, it authorized EUFOR to be the legal successor to SFOR and to carry out a peace stabilization role for an initial period of one year. At a ceremony in Sarajevo on December 2, NATO formally concluded the SFOR mission and the EU launched Operation Althea . On November 21, 2005, the U.N. Security Council passed Resolution 1639, which authorized EUFOR and the NATO Headquarters in Bosnia for a further twelve months. On November 21-22, the EU Council took several decisions on the EU's relationship with Bosnia including opening Stabilization and Association Agreement negotiations, continuing an EU police mission in Bosnia, and keeping an EU military presence in Bosnia at basically unchanged force levels for the coming year. On November 13, 2006, EU foreign and defense ministers considered a proposal to reduce EUFOR's troop strength based on a positive evaluation of the security situation. However, ministers postponed a decision to cut EUFOR reportedly in consideration of Kosovo's status process and potential for regional unrest. On November 21, the U.N. Security Council further extended EUFOR's and NATO's mandates in Bosnia until November 2007 in Resolution 1722. The EU on February 27, 2007, confirmed an earlier decision in principle to reconfigure EUFOR and reduce its size from 6,500 to 2,500 troops by the end of May. The reconfiguration was completed by August. On November 21, the U.N. Security Council passed Resolution 1785 that further extended EUFOR's and NATO's mandates in Bosnia for another year. On December 10, the EU welcomed the successful reconfiguration of EUFOR and agreed to retain a military presence in Bosnia for as long as was necessary.

Summary:
On December 2, 2004, NATO formally concluded its Stabilization Force (SFOR) mission in Bosnia and Herzegovina and handed over peace stabilization duties to a European Union force (EUFOR). The mission of the EU's Operation Althea has been to ensure continued compliance with the 1995 Dayton peace agreement and contribute to a secure environment and Bosnia's efforts towards European integration. In 2007, the EU carried out a reconfiguration of EUFOR that reduced its strength from 6,500 to around 2,500 troops. NATO retains a small headquarters presence in Sarajevo to provide advice on defense reforms and to support counterterrorism efforts and the apprehension of wanted war crimes suspects believed to be hiding in or transiting through Bosnia. In November 2007, the U.N. Security Council extended the EU and NATO mandates in Bosnia for another year. This report will no longer be updated. See also CRS Report RS22324, Bosnia: Overview of Current Issues, by [author name scrubbed].