The U.S. Congress has expressed deep concern over Russia's annexation of Crimea and its role in the ongoing crisis in Ukraine. Among other things, the crisis has heightened concerns in the United States and in Europe about the future direction and scope of the transatlantic security relationship and the cornerstone of that relationship, the North Atlantic Treaty Organization (NATO). Some policy makers and analysts have called for a reassessment of the transatlantic community's progress in realizing its goal of a Europe "whole, free, and at peace," citing security concerns in some of NATO's Central and Eastern European member states and ongoing territorial disputes in countries on the alliance's borders, such as Moldova, Ukraine, and Georgia. Questions about NATO's commitment and capacity to defend its member states and about the nature of the alliance's relationship with Russia have moved to the forefront of discussions about NATO's future. These questions are expected to feature prominently at NATO's next summit of heads of state and government, scheduled to take place in Wales on September 4-5, 2014. The crisis in Ukraine has also exposed longer-standing tensions within NATO regarding its strategic focus. Since the end of the Cold War, NATO has evolved from an exclusive focus on territorial defense and deterrence in Europe to overseeing a range of military and crisis management operations across the globe. This transformation was predicated largely on the perception that Russia no longer posed a security threat to NATO, and on a conviction that the primary security challenges facing the allies emanated from beyond the Euro-Atlantic region. However, some NATO members, including many former members of the communist bloc, have consistently expressed concern that the alliance's transformation could come at the expense of its capacity to uphold its commitment to collective defense, enshrined in Article 5 of the North Atlantic Treaty. After more than a decade of war in Afghanistan and against the backdrop of a militarily resurgent Russia, some allies are calling for a renewed NATO focus on collective defense. Debates about NATO's mission come against the backdrop of continued economic stagnation in Europe and long-standing U.S. concerns about a downward trend in European defense spending, shortfalls in European defense capabilities, and burden sharing within the alliance. In 2013, total defense spending by NATO European allies as a percentage of GDP was about 1.6%; and just three NATO allies (Greece, the UK, and the United States) exceeded the alliance's goal of spending 2% of GDP on defense. Since 2001, the U.S. share of total allied defense spending has grown from 63% to 72%. Analysts in the United States have long asserted that defense spending in many European countries is inefficient, with disproportionately high personnel costs coming at the expense of much-needed research, development, and procurement. In 2013, only four allies met a NATO guideline to devote 20% of defense expenditures to the purchase of major equipment, considered a key indicator of the pace of military modernization. These trends correlate with significant shortfalls in key military capabilities, including strategic air- and sealift; aerial refueling; and intelligence, surveillance and reconnaissance (ISR). NATO Secretary General Anders Fogh Rasmussen and others have argued that the budgetary constraints facing allied governments could spur much-needed defense cooperation among European allies. At NATO's May 2012 summit, the allies committed to a "Smart Defense" initiative that calls for cooperation, prioritization, and specialization in pursuit of needed defense capabilities. Some critics maintain that this is just the latest in a long line of post-Cold War efforts to enhance capabilities that have had mixed success, at best. They argue that the limited outcomes may reflect a general lack of public support for military engagement and divergent threat perceptions both across the Atlantic and within Europe. As noted above, within Europe, some allies have emphasized the need for territorial defense capabilities, while others have stressed the importance of more flexible, rapidly deployable units and civilian-military crisis management operations. An increasingly strained budget environment and heightened concerns about the security threat from Russia appear to be amplifying these differences. U.S. officials have consistently underscored their firm commitment to the transatlantic security relationship and the collective defense of the alliance. However, far-reaching defense budget cuts in the United States, the Obama Administration's "rebalance" to Asia, and the withdrawal over the past two years of two of the U.S. Army's four Brigade Combat Teams based in Europe have raised questions about future U.S. commitments to European security. Russia's actions in Ukraine have heightened these concerns. Reflecting the views of the United States and its European allies, NATO Secretary General Rasmussen has characterized Russia's military aggression as "the most serious crisis in Europe since the fall of the Berlin Wall," and declared that NATO can "no longer do business as usual with Russia." NATO's response to the crisis thus far has focused on demonstrating support for Ukraine and its territorial integrity; reaffirming the allied commitment to defensing Central and Eastern European allies; and rebuking Russia. In early April, NATO announced the suspension of all "practical" civilian and military cooperation with Russia in the framework of the NATO-Russia Council. Political dialogue between the two sides will continue. Cooperative activities in the NATO-Russia Council that could be affected include a helicopter maintenance fund and a counternarcotics initiative in Afghanistan, and some joint counter-terrorism initiatives. The allies have agreed to strengthen political and military cooperation with the government in Kyiv. This includes providing military trainers to assist in Ukraine's military modernization efforts and improving the interoperability of Ukrainian and allied armed forces through exercises and joint operations. In June, Secretary General Rasmussen announced the creation of several new NATO trust funds to help develop Ukrainian defense capacity, including in the areas of logistics, command and control, cyber defense, and assisting retired military personnel to adapt to civilian life. Total contributions to these trust funds has not as yet been publicly disclosed. NATO has not provided Ukraine with military hardware and is not expected to do so. This does not, however, preclude bilateral military assistance from individual allies. For example, as discussed below, the United States has provided Ukraine with non-lethal military aid (see, " Ukraine "). All NATO allies have thus far ruled out providing Ukraine with lethal military aid, arguing, among other things, that such assistance could lead to a further escalation of the conflict. Since Russia's annexation of Crimea, NATO has sought to reinforce its commitment to defending central and eastern European allies. Measures taken thus far have centered on air defense and surveillance, maritime deployments, and military exercises. Despite calls from some member states, NATO has thus far ruled out permanent troop deployments in the region. Air Defense and Surveillance: NATO member states have deployed additional fighter jets to the alliance's Baltic Air Policing mission and NATO is carrying out aerial surveillance flights over Poland and Romania. In April, NATO increased the Air Policing Mission from four to 16 fighter jets. The mission to protect Baltic airspace has been led by NATO allies on a rotational basis since 2004 (the Baltic countries do not have their own air forces). Denmark, France, Poland, and the UK are each currently contributing four fighter aircraft to the mission. Canada has also deployed jets to Romania to conduct training exercises with the Romanian air force. Since mid-March 2014, NATO airborne warning and control system (AWACS) surveillance aircraft have been conducting twice daily flights to monitor events in Ukraine, one over Poland and one over Romania. NATO has used surveillance images to monitor Russian troop movements along the Ukrainian border. Maritime deployments: NATO has deployed two maritime groups on patrols to the Baltic and Mediterranean Seas. One group of 5-7 mine clearance vessels has been patrolling the Baltic Sea since late April. It includes ships from Belgium, Estonia, France, Germany, the Netherlands, and Norway. A second maritime contingent of frigates has been patrolling the Mediterranean since May. It includes ships from Canada, Germany, Norway, Turkey, and the United States. In mid-July, a third NATO maritime group participated in naval exercises in the Black Sea. The group of four ships (from Italy, Turkey, and the UK) conducted interoperability exercises with naval units from Greece, Italy, Romania, Turkey, and the United States. Military Exercises: NATO member states have conducted several military exercises in Central and Eastern Europe, and have planned at least one major exercise in Ukraine in September. From May 16-23, about 6,000 allied troops conducted a military exercise in Estonia aimed at repelling a potential attack on Estonian territory. Troops from Belgium, Denmark, Estonia, France, Latvia, Lithuania, Poland, the UK, and the United States participated in the NATO exercise, dubbed "Steadfast Javelin 1." The U.S. Army-led Rapid Trident 2014, originally scheduled to take place in western Ukraine in July, has been tentatively postponed until mid-September. The Army anticipates that up to 14 nations, including many NATO member states, will participate in the exercise, which will reportedly feature a combined U.S.-Ukrainian battalion headquarters practicing a peacekeeping operation. Last year's Rapid Trident exercise in Ukraine included 1,300 troops from 17 nations. Although they have welcomed these measures, some allies in Central and Eastern Europe have called for a more robust demonstration of NATO's willingness and capacity to defend them. Most notably, leaders in Poland and the Baltic State have advocated permanent NATO troop deployments on their territories (see " Security Situation and Concerns in Central and Eastern Europe "). Other allies have cautioned against a further "militarization" of NATO relations with Russia, highlighting, among other things, NATO's 1997 pledge to refrain from permanently stationing substantial combat forces in countries that joined NATO after the collapse of the Soviet Union.