Operation Deny Flight was a North Atlantic Treaty Organization (NATO) operation that began on 12 April 1993 as the enforcement of a United Nations (UN) no-fly zone over Bosnia and Herzegovina. The United Nations and NATO later expanded the mission of the operation to include providing close air support for UN troops in Bosnia and carrying out coercive air strikes against targets in Bosnia. Twelve NATO members contributed forces to the operation and, by its end on 20 December 1995, NATO pilots had flown 100,420 sorties.
The operation played a noticeable role in shaping both the Bosnian War and NATO. The operation included the first combat engagement in NATO's history, a 28 February 1994 air battle over Banja Luka, and in April 1994, NATO aircraft first bombed ground targets in an operation near Goražde. Cooperation between the UN and NATO during the operation also helped pave the way for future joint operations. Although it helped establish UN–NATO relations, Deny Flight led to conflict between the two organizations. Most notably, significant tension arose between the two after UN peacekeepers were taken as hostages in response to NATO bombing.
The operations of Deny Flight spanned more than two years of the Bosnian War and played an important role in the course of that conflict. The no-fly zone operations of Deny Flight proved successful in preventing significant use of air power by any side in the conflict. Additionally, the air strikes flown during Deny Flight led to Operation Deliberate Force, a massive NATO bombing campaign in Bosnia that played a key role in ending the war.
Background and Operation Sky Monitor
In October 1992, at the beginning of the Bosnian War, the United Nations Security Council passed Resolution 781. This resolution prohibited unauthorized military flights in Bosnian airspace. Following the resolution, NATO began Operation Sky Monitor during which NATO forces monitored violations of the no-fly zone, without taking any military action against violators. By April 1993, NATO forces had documented more than 500 violations of the no-fly zone. In response to these "blatant" violations of Bosnian air space, and implicitly of resolution 781, the UN Security Council issued Resolution 816.
While Resolution 781 prohibited only military flights, Resolution 816 prohibited all flights in Bosnian air space, except for those expressly authorized by the UN Flight Coordination Center in Zagreb. The resolution also authorized UN member states to "take all necessary measures ... to ensure compliance" with the no-fly zone restrictions. In response to this resolution, NATO commenced Operation Deny Flight on 12 April 1993. Initially Deny Flight was intended only to enforce the no-fly zone; however several NATO members , including the United States, were eager to find ways to end the war and improve the situation of civilians, and hoped that military action could do so. The US had already taken unilateral actions to aid civilians caught in the conflict by dropping humanitarian supplies into Bosnia under Operation Provide Promise, and many US officials argued for the use of military force. These officials were eager to expand US air operations through Deny Flight, hoping that an aggressive no-fly zone and possible air strikes would end the conflict more quickly. NATO forces suffered its first loss on the second day of operations, when a French Mirage 2000 crashed in the Adriatic Sea due to mechanical failure. The pilot ejected safely.
Enforcement of no-fly zone
After its adoption, Operation Deny Flight was relatively successful in preventing fixed-wing aircraft from flying over restricted air space in Bosnia. During the monitoring phase of Operation Sky Monitor, unauthorized fixed-wing flights averaged twenty per month, but during Deny Flight, the average was three. During the conflict, there were only an estimated 32 fixed-wing military aircraft in Bosnia, all of them former Yugoslav Air Force planes under the control of the Bosnian Serbs. Thus, NATO primarily needed to prevent incursions into Bosnian airspace from Croatia and Serbia.
The first serious violation to the no-fly zone came on 28 February 1994, when six Serb J-21 Jastreb jets bombed a Bosnian factory. US Air Force F-16s shot down four of the six Serb jets over Banja Luka. This engagement was the first combat engagement of Operation Deny Flight, and its only significant air-to-air combat engagement. Perhaps more importantly, the Banja Luka incident was also the first combat engagement in the history of NATO. The Serbs acknowledged the loss of a fifth aircraft in the incident.
While Deny Flight was relatively successful in stopping flights of fixed-wing aircraft, NATO forces found it very difficult to stop helicopter flights, which presented a more complicated challenge. All sides in the conflict used helicopters extensively for non-military purposes, and some of these flights were authorized by the UN. Under the operation's rules of engagement, NATO fighters were only authorized to shoot down helicopters that committed a hostile act. Otherwise, NATO fighters issued orders to "land or exit", in other words, land the aircraft or leave the no-fly zone. Typically, helicopters in Bosnian airspace complied with these orders by landing, but then took off again after NATO forces departed. None of the parties in the conflict respected the ban on helicopter flights, as evidenced when Ratko Mladić responded to a BBC journalist's question about his violation of the ban with the statement, "The commander of the Bosnian Serb armed forces does not ride on a donkey."
Deceptive markings on helicopters further complicated matters for NATO pilots. Many of the combatants painted their helicopters to look like those of organizations that the UN's Zagreb Flight Coordination Center had authorized to fly in restricted space. For example, the army of the Republika Srpska often painted a Red Cross logo on their helicopters, and Croatian helicopters were given markings similar to those of UN humanitarian aid helicopters. The questionable identity of these helicopters became particularly problematic after the Black Hawk Incident in Iraq, because NATO pilots became more reluctant to engage potential belligerents without clear identification. As a result of the rules of engagement and difficulties in aircraft identification, NATO forces proved unable to stop most unauthorized helicopter flights, resulting in a documented total of 5711 unauthorized flights during the conflict.
Close air support and air strikes
Even before Operation Deny Flight began, a number of US officials lobbied for a large role for NATO air power in Bosnia. In particular, as part of Bill Clinton's platform during his 1992 campaign for President of the United States he promised a "lift and strike" policy, which included the use of air strikes against Bosnian Serb forces. After the commencement of Operation Deny Flight, US officials, including President Clinton, pushed for an expanded mission. After the Bosnian Serbs rejected the Vance-Owen Plan on 6 May 1993, Clinton and other US officials intensified these calls and they discussed the possibility of using large-scale strikes to coerce the Serbs into acceptance. Ultimately, no such strikes were approved or carried out, but American officials became more open to the idea of using air power for coercion.
In June 1993, partly in response to pressure from the United States, the Security Council passed Resolution 836 which authorized NATO forces to provide close air support for UNPROFOR forces upon request. The procedure to request air support was quite difficult, as it involved the "dual key" of both UN and NATO approval. UN approval required contact with the United Nations headquarters in New York City, making effective coordination nearly impossible given the difference in time zones. The UN approval process was later somewhat streamlined when UN Secretary-General Boutros Boutros-Ghali delegated the authority to authorize air strikes to his special representative in Bosnia, Yasushi Akashi. Even after this simplification, however, "dual key" remained a problem as all requests first had to be processed through the UN Air Operations Center in Kiseljak then pass up the entire UNPROFOR chain of command to Akashi. After Akashi approved the request, he would make a request to NATO commanders who then had to pass orders back down their chain of command and coordinate with forces on the ground.
Due to the difficult "dual key" authorization measure, NATO did not fulfill its close air support mission for several months. Nonetheless, NATO soon began further planning for a third mission: coercive air strikes as advocated by the United States. NATO first prepared to use Deny Flight to carry out air strikes in August 1993 as part of a plan to end the Siege of Sarajevo. After diplomatic intervention, the plan was not executed, but a precedent was established for the possible use of air strikes. Thus, in February 1994, after the Sarajevo Marketplace Bombing, NATO issued an ultimatum to the Serbs to withdraw all heavy weapons from an exclusion zone around Sarajevo or face bombing. The Bosnian Serbs complied with NATO demands and no strikes were carried out.
1994 Serb Jastreb J-21 shootdown
On 28 February 1994, a NATO Airborne Early Warning aircraft flying over Hungary vectored two US F-16s to an area south of Banja Luka, where six J-21 Jastreb and two J-22 Orao were flying back to their base after bombing the "Bratstvo" military factory at Novi Travnik, in blatant violation of the non-fly zone. Four Serb Jastrebs were shot down and another crashed while trying to escape in low-level flight. This marked the first combat mission in NATO's history. Eight days later, on 8 March, a Spanish Air Force CASA C-212 transport plane was hit by a missile near the border between Croatia and the Republic of Krajina, while ferrying UNPROFOR personnel from Zagreb to Split. The crew managed to land the aircraft at Rijeka. The attack may have been a Bosnian Serb response to the 28 February shootdowns.
Attack on Goražde
In April 1994, Bosnian Serbs forces launched an attack on the UN Safe Area of Goražde. Initially, US Secretary of Defense William Perry told reporters that the United States would "not enter the war to stop" the Serbs from overrunning Goražde, and other senior officials publicly downplayed the possibility of using air strikes. Several days into the attack, however, a number of UNPROFOR soldiers were injured, and one was killed by Serb fire. Thus, General Michael Rose, the UNPROFOR Commander, requested NATO strikes under the mandate of UNSCR 836.
On 10 April, in response to the request, two US Air Force F-16s dropped 4 bombs on Serb targets, including a tank and a command post. The next day, two US Marine Corps F/A-18C aircraft strafed additional targets in the area. That same day, General Ratko Mladić, the commander of the Bosnian Serb army, called General Rose and threatened the safety of his forces, saying "one more attack and I will shoot down aircraft – cannot guarantee safety of UNPROFOR and will attack UNPROFOR and your headquarters". Making good on his threat, from 12 April to 14 April, Mladić ordered his forces to surround 150 UNPROFOR peacekeepers, effectively taking them hostage. Mladić then telephoned General Rose and told him "that if NATO did not stop its actions, not one UN soldier would leave alive". Some of the UNPROFOR hostages were from NATO member states, notably the United Kingdom and France, who pushed for an immediate end to the strikes out of fear for the safety of their personnel. In response to the British and French concerns, NATO temporarily recalled its forces, but on 15 April, in response to increased Serb attacks, aircraft were again deployed to the area.
As Mladić had promised, the Bosnian Serb army around Goražde attempted to shoot down NATO aircraft. On 15 April 1994, a French Dassault Étendard IV jet was hit by ground fire while conducting a reconnaissance mission in the area. The jet was damaged, but returned safely to its carrier, the Clemenceau. On 16 April, a British Sea Harrier from the carrier HMS Ark Royal was called in by UN forces to strike a tank. After making several unsuccessful passes at the target, the Sea Harrier was targeted by a Bosnian Serb shoulder-launched surface-to-air missile and was subsequently shot down. The pilot ejected and was successfully repatriated. After the Harrier shootdown, NATO did not carry out any further strikes around Goražde, and on 17 April, Mladić released most of the hostages he had taken. Over the next several days, the Serbs agreed to, and then broke, several ceasefires in the Goražde area. In an effort to secure Goražde and to force the Serbs to honor agreements, NATO and the UN issued an ultimatum for Bosnian Serb forces to cease their attacks and withdraw their forces or face additional air strikes on 22 April. The Serbs complied with the ultimatum, requiring a withdrawal of heavy weapons from a 20 kilometers (12 mi) zone and all forces from a 3 km (1.9 mi) zone. Because of the Serb compliance, NATO ceased its operations around Goražde.