Operation Active Endeavour (2001-2016)

  • Last updated: 01 Sep. 2022 16:05

Under Operation Active Endeavour, NATO ships patrolled the Mediterranean and monitored shipping to help deter, defend, disrupt and protect against terrorist activity. The operation evolved out of NATO’s immediate response to the terrorist attacks against the United States of 11 September 2001.


  • Operation Active Endeavour was one of eight initiatives launched in response to the 9/11 terrorist attacks against the United States in 2001. It was terminated in October 2016 and succeeded by Sea Guardian.
  • It helped deter terrorist activity in the Mediterranean Sea.
  • By tracking and controlling ships, Active Endeavour also helped secure one of the busiest trade routes in the world.
  • The operation evolved from a platform-based to a network-based operation, using a mix of on-call units and surge operations instead of deployed forces.
  • The experience accrued through Active Endeavour gave NATO unparalleled expertise in deterring maritime terrorist activity in the Mediterranean, especially with regard to the proliferation and smuggling of weapons of mass destruction and cooperation with non-NATO countries and civilian agencies.
  • Initially an Article 5 operation, Active Endeavour benefitted from support from non-NATO countries from 2004 onwards.
  • The aim of the operation and its current functions

    Operation Active Endeavour (OAE) is the only Article 5 operation on anti-terrorism that NATO has ever had. It was initiated in support of the United States immediately after 9/11. It aimed to demonstrate NATO's solidarity and resolve in the fight against terrorism and help deter and disrupt terrorist activity in the Mediterranean.

    NATO forces hailed over 128,000 merchant vessels and boarded some 172 suspect ships. By conducting these maritime operations against terrorist activity, NATO’s presence in these waters benefited all shipping travelling through the Straits of Gibraltar by improving perceptions of security. NATO helped to keep seas safe, protect shipping and control suspect vessels. Moreover, this operation also enabled NATO to strengthen its relations with partner countries, especially those participating in the Alliance’s Mediterranean Dialogue.

    Keeping seas safe and protecting shipping

    Keeping the Mediterranean’s busy trade routes open and safe is critical to NATO’s security. In terms of energy alone, some 65 per cent of the oil and natural gas consumed in Western Europe passes through the Mediterranean each year, with major pipelines connecting Libya to Italy and Morocco to Spain. For this reason, NATO ships systematically carried out preparatory route surveys in “choke” points as well as in important passages and harbours throughout the Mediterranean.

    Tracking and controlling suspect vessels

    From April 2003, NATO systematically boarded suspect ships. These boardings took place with the compliance of the ships’ masters and flag states in accordance with international law.

    What happened in practice was that merchant ships passing through the eastern Mediterranean were hailed by patrolling NATO naval units and asked to identify themselves and their activity. This information was then reported to NATO’s Maritime Commander in Northwood, the United Kingdom. If anything appeared unusual or suspicious, teams of between 15 and 20 of the ships’ crew boarded vessels to inspect documentation and cargo. Compliant boarding could only be conducted with the consent of the flag state and/or the ship’s master. NATO personnel could otherwise convey this information to the appropriate law enforcement agency at the vessel’s next port of call. The suspect vessel was then shadowed until action was taken by a responsible agency/authority, or until it entered a country’s territorial waters.

    Unexpected benefits

    While the mandate of OAE was limited to deterring, defending, disrupting and protecting against terrorist-related activity, the operation had a visible effect on security and stability in the Mediterranean that was beneficial to trade and economic activity.

    NATO ships and helicopters also intervened on several occasions to rescue civilians on stricken oil rigs and sinking ships, saving the lives of several hundred people over time. The operation provided the framework for the maritime component of NATO’s assistance to the Greek government to ensure the safe conduct of the 2004 Olympic and Paralympic Games in August and September 2004. Task Force Endeavour conducted surveillance, presence and compliant boarding operations in international waters around the Greek peninsula with Standing Naval Forces surface ships, supported by maritime patrol aircraft and submarines and in coordination with the Hellenic Navy and Coast Guard.

    Closer cooperation with partners

    The increased NATO presence in the Mediterranean also enhanced the Alliance’s security cooperation programme with seven countries in the wider Mediterranean region – Algeria, Egypt, Israel, Jordan, Mauritania, Morocco and Tunisia. This programme - the Mediterranean Dialogue - was set up in 1994 to contribute to regional security and stability and to achieve better mutual understanding between NATO and its Mediterranean partners.

    Mediterranean Dialogue countries are equally concerned by the threat of terrorism and cooperated with NATO in OAE by providing intelligence about suspicious shipping operating in their waters.

  • Command and structure of the operation

    The operation was under the overall command of, and was conducted from, Maritime Command Headquarters, Northwood, United Kingdom, through a task force deployed in the Mediterranean.

    Task Force Endeavour consisted of a balanced collection of surface units, submarines and maritime patrol aircraft. The operation also regularly made use of NATO’s two high-readiness frigate forces, which are permanently ready to act and capable of conducting a wide range of maritime operations.

    The operational pattern used surface forces as reaction units to conduct specific tasks such as locating, tracking, reporting and boarding of suspected vessels in the light of intelligence.

    NATO’s Standing Naval Forces rotated in providing periodic support to OAE either through “surges” (when an entire force participates) or through individual units being put on call at times when the operation had no assigned forces.

  • Evolution

    An Article 5 deployment

    The deployment was one of eight measures taken by NATO to support the United States in the wake of the terrorist attacks of 11 September 2001, following the invocation of Article 5, NATO’s collective defence clause, for the first time in the Alliance’s history.

    The deployment started on 6 October and was formally named Operation Active Endeavour on 26 October 2001. Together with the dispatch of Airborne Warning and Control System (AWACS) aircraft to the United States, it was the first time that NATO assets were deployed in support of an Article 5 operation.

    From October 2001, NATO ships patrolled the Mediterranean and monitored shipping, boarding any suspect ships. Compliant boarding operations were essential to the successful continuation of the operation. They were limited to trying to establish whether a vessel was engaged in terrorist activity.

    In March 2003, OAE was expanded to provide escorts through the Straits of Gibraltar to non-military ships from Alliance member states requesting them. This extension of the mission – Task Force STROG (Straits of Gibraltar) – was designed to help prevent terrorist attacks such as those off Yemen on the USS Cole in October 2000 and on the French oil tanker Limburg two years later. The area was considered particularly vulnerable because the Straits are extremely narrow and some 3,000 commercial shipments pass through daily. In total, 488 ships took advantage of NATO escorts until this mission was suspended in May 2004. Forces remained ready to move at 30 days’ notice.

    Covering the entire Mediterranean

    One year later, in March 2004, as a result of the success of OAE in the Eastern Mediterranean, NATO extended its remit to the whole of the Mediterranean.

    At the June 2004 Istanbul Summit, Allied leaders decided to enhance OAE. They also welcomed offers by partner countries to support the operation.

    An evolving operation

    In the revised Concept of Operations – approved by the North Atlantic Council on 23 April 2009 – the Military Committee highlighted two considerations: the need to further enhance information-sharing between NATO and other actors in the region; the fact that in some cases, the operation was hampered by the lack of consent to conduct compliant boarding of suspect vessels.

    In addition, the Operational Plan – approved in January 2010 – shifted OAE from a platform-based to a network-based operation, using a combination of on-call units and surge operations instead of deployed forces; it also increased cooperation with non-NATO countries and international organisations in order to improve Maritime Situational Awareness. All options for future changes in the operation’s mandate were considered on the basis of the Alliance Maritime Strategy, adopted in January 2011. OAE fulfilled the four roles outlined in this strategy: deterrence and collective defence; crisis management; cooperative security; and maritime security.

    In February 2013, as a result of the reform of the military command structure initiated in 2011, the operation changed command. Initially, OAE was under the overall command of Joint Force Command (JFC), Naples, and was conducted from Allied Maritime Component Command Naples, Italy (CC-Mar Naples). From 22 February 2013, it came under the command of, and was conducted by, Maritime Command Headquarters (HQ MARCOM), Northwood.

    As the Alliance refined its counter-terrorism role over the years, the operation’s remit was extended and its mandate regularly reviewed. In addition to tracking and controlling suspect vessels to keep the seas safe, it also aimed to build a picture of maritime activity in the Mediterranean. To do this, the ships conducted routine information approaches to various vessels in order to reassure and inform mariners on the efforts to keep the maritime community safe.

    The experience that NATO accrued in Active Endeavour gave the Alliance unparalleled expertise in the deterrence of maritime terrorist activity in the Mediterranean Sea. This expertise was relevant to wider international efforts to combat terrorism and, in particular, the proliferation and smuggling of weapons of mass destruction, as well as enhanced cooperation with non-NATO countries and civilian agencies. OAE was terminated in October 2016 when Sea Guardian became operational. At the Warsaw Summit in July 2016, NATO leaders agreed to create a broader maritime operation in the Mediterranean. Sea Guardian is a flexible maritime operation that is able to perform the full range of maritime security tasks, if so decided by the North Atlantic Council.  It is currently performing three tasks in the Mediterranean Sea: maritime situational awareness, counter-terrorism at sea and support to capacity-building.

  • Contributing countries

    Because it was an Article 5 operation, Operation Active Endeavour initially involved member countries only. Some NATO members, mainly Greece, Italy, Spain and Turkey contributed directly to the operation with naval assets. Escort operations in the Straits of Gibraltar used to involve the use of fast patrol boats from northern European Allies Denmark, Germany and Norway. Spain also provided additional assets in the Straits. OAE relied heavily on the logistic support of Mediterranean NATO Allies.

    From 2004, partner and non-NATO countries started offering their support.

    All offers were considered on a case-by-case basis. Exchanges of Letters were signed between NATO and Israel, Morocco, Russia and Ukraine. In addition, Finland and Sweden informally expressed their interest in contributing to the operation. Georgia and Israel sent liaison officers to HQ MARCOM in Northwood following the signing of tactical Memoranda of Understanding with NATO on the exchange of information. Russia deployed vessels twice, in 2006 and 2007, and Ukraine a total of six times since 2007. New Zealand also deployed a vessel (April-May 2015).