The 1995 Dayton peace agreement ended a 3 ½-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.