Cover: Operation Allied Force

Operation Allied Force

Lessons for the Future

Published 2001

by Benjamin S. Lambeth

Research Brief

On March 24, 1999, NATO forces initiated an air war against Serbia in an effort to put an end to the human rights abuses that were then being perpetrated against the ethnic Albanian population in Kosovo. This bombing effort, code-named Operation Allied Force, ended 78 days later with the capitulation of Yugoslavia's president, Slobodan Milosevic, and the subsequent withdrawal of Serbian army and paramilitary forces from Kosovo. Yet despite its success in bringing about Milosevic's defeat, Operation Allied Force was a suboptimal use of air power to resolve a regional conflict. Although NATO's air offensive ultimately proved crucial to Milosevic's decision to submit to NATO's terms, a host of deficiencies—both strategic and operational—protracted the air effort and hampered its overall effectiveness. Figure 1 shows a map of the immediate area of operations.

In NATO's Air War for Kosovo: A Strategic and Operational Assessment, RAND researcher Benjamin S. Lambeth offers a thorough appraisal of Operation Allied Force, with a view toward shedding light both on the operation's strengths and on its most salient weaknesses. After outlining the main highlights of NATO's air offensive, the study examines the various factors that interacted to induce Milosevic to capitulate when he did. It then explores air power's most notable accomplishments in Allied Force, as well as the many problems and sources of friction that hindered the operation both in its planning and in its execution. Finally, the report assesses Operation Allied Force from a political and strategic perspective, calling attention to those issues that are likely to have the greatest bearing on future military policymaking.

Figure 1. The Operations Arena

Why Milosevic Conceded: A Step Back

Although NATO's bombing effort in the end played the determining role in bringing about Milosevic's defeat, a host of additional factors also figured importantly in this respect. In addition to the damage that was being wrought by NATO's air attacks, for example, another factor that very likely contributed to Milosevic's surrender was the sheer depravity of Serbia's conduct in Kosovo, which ultimately stripped it of what little remained of international support, most notably from the Russians. Yet another element that may have come into play was pressure from Yugoslavia's elite, for whom NATO's bombing of key industrial and economic interests in and around Belgrade had begun to take an intensely personal toll.

Milosevic was, in addition, almost surely aware of the growing potential for a ground invasion as NATO's air war progressed. By the end of May 1999, it had become clear that NATO had increasingly accepted the need to go ahead with a ground invasion in the event that its air effort alone failed to bring about a decisive outcome. Although senior officials in Washington remained highly resistant to proceeding with that course right up the very end, Milosevic cannot have failed to apprehend the implications of such a possibility.

At the same time, Milosevic was bearing witness to an escalating air war that showed no signs of abating (Figure 2). Although NATO's efforts to find and attack dispersed and hidden enemy forces in Kosovo had proved largely ineffective, an increasing number of infrastructure targets were being hit each day, and these attacks were taking a mounting toll both on Yugoslavia's leadership and on the population as a whole. It is thus likely that NATO's air offensive ultimately convinced Milosevic that the alliance not only intended to persist in its attacks but was determined to prevail. In the end, the sustained bombing, although by no means the sole factor responsible for the success of Allied Force, set the stage for Milosevic's capitulation by making it clear that he had little to gain by holding out.[1]

Figure 2. Conflict Timeline

Operational Issues: The Air War in Action

Much of the controversy surrounding Operation Allied Force has pivoted on the discrepancy between what the NATO allies expected and what they ultimately encountered. Although NATO initially sought to neutralize Serbia's air defenses, the alliance soon discovered that the Serbs kept most of their surface-to-air missiles dispersed with their radars not emitting, rendering them difficult to find and attack. At the same time, the Serbs' heavy man-portable air defenses and antiaircraft artillery forced NATO aircrews to conduct bombing attacks from an altitude of 15,000 ft or higher, which sometimes hampered the visual identification of targets and successfully distinguishing between military convoys and civilian refugees.

Mobile enemy troops in Kosovo also proved to be more capable and tenacious foes than had been anticipated. Operating under the cover of inclement weather and shielded by mountainous terrain, Serb forces were frequently able to disperse and conceal their weapons, thereby eluding allied efforts to find and attack them in a timely way. This shortcoming protracted the overall allied effort, eventually occasioning a more determined pursuit of infrastructure targets in and around Belgrade.

Despite unprecedented pressure to avoid civilian casualties and unintended collateral damage, Operation Allied Force also fell prey to a number of bombing errors, including the widely publicized inadvertent bombing of the Chinese embassy in Belgrade. Although some of these errors were a natural consequence of NATO-imposed operational constraints and Serbia's uncongenial spring weather, the extraordinary media attention that was paid to them further detracted from the overall effectiveness of the campaign by starkly showing what can happen when achieving zero collateral damage becomes not just a desired goal of allied strategy but also the expectation.

Strategic Issues: An Overview

Operation Allied Force left in its wake a number of questions regarding its overall strategy and execution. To begin with, allied planners erred badly at the very outset of the campaign by failing to appreciate Kosovo's profound historical and cultural significance to the Serbs. This critical error in judgment led to the allies' flawed assumption that Milosevic would capitulate to NATO demands without the need for an aggressive or protracted engagement.

NATO's operation in Kosovo was further hampered by the need to achieve consensus among its politically diverse member states, many of which were hesitant to use significant force in what was essentially a humanitarian operation. This requirement for unanimity on at least the basics of allied strategy led not only to the outright rejection of a ground option from the very start but also to the imposition of exceptionally stringent rules of engagement. Added to this mix of coalition restraints were internal disagreements within the U.S. component of the alliance over target priorities and broader force employment strategy, which further undermined the effectiveness of NATO's efforts.

NATO's Air War in Perspective

Operation Allied Force was the most intense and sustained military operation to have been conducted in Europe since the end of World War II. It also represented the first extended use of military force by NATO as well as the first time air forces had successfully coerced an enemy leader in the absence of significant friendly ground-force involvement. Although the operation failed to halt Milosevic's ethnic cleansing campaign, it succeeded in reversing that campaign by forcing Milosevic to accede to NATO's demands.

At the same time, NATO's air war suffered from a number of critical shortcomings. On an operational level, the allies' attempts to find and attack dispersed and hidden enemy ground forces in Kosovo proved largely unsuccessful, enabling Milosevic to accelerate his ethnic cleansing campaign against the Kosovar Albanians even as NATO's bombing efforts intensified. On a strategic level, the operation's desultory onset, restrictive rules of engagement, and ill-conceived strategy hobbled the allies' effort by compromising their ability to engage a wily and determined foe. In the end, Operation Allied Force's most noteworthy distinction may lie in the fact that the bombing effort prevailed despite the myriad impediments it faced. In light of that, perhaps the most telling lesson to be drawn from Operation Allied Force is that however capable air forces may have become in principle compared to other force elements, they can never be more effective than the strategy they are intended to support.


  • [1] For a fuller treatment of this thesis, see Stephen T. Hosmer, The Conflict Over Kosovo: Why Milosevic Decided to Settle When He Did, RAND, MR-1351-AF, 2001.

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