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{{Short description|Passages between the northern Atlantic Ocean and the Norwegian Sea}}
{{Use dmy dates|date=August 2021}}
{{More citations needed|date=February 2008}}

[[Image:GIUK gap.png|thumb|upright=1.35|The GIUK gap in the North [[Atlantic]] (showing international boundaries as of 1983) ]]The '''GIUK gap''' (sometimes written G-I-UK) is an area in the northern Atlantic Ocean that forms a [[naval warfare|naval]] [[choke point]]. Its name is an [[acronym]] for ''[[Greenland]], [[Iceland]]'', and the ''[[United Kingdom]]'', the gap being the two stretches of open ocean among these three landmasses. It separates the [[Norwegian Sea]] and the [[North Sea]] from the open [[Atlantic Ocean]]. The term is typically used in relation to military topics. The area has for some nations been considered strategically important since the beginning of the 20th century.<ref>{{Cite journal|last=Pincus|first=Rebecca|date=27 May 2020|title=Towards a New Arctic|journal=The RUSI Journal|volume=165|issue=3|pages=50–58|doi=10.1080/03071847.2020.1769496|s2cid=219741469|issn=0307-1847}}</ref>

==History==
Since the beginning of the 20th century, the exploitation of the GIUK gap by northern forces and measures to patrol and secure the gap by opposing forces have played an important role in naval and in overall military planning.{{citation needed|date=August 2020}}

===World War II===
From the start of [[World War II]] in 1939, German ships used the gap to break out from their bases in northern Germany (and from [[German U-boat bases in occupied Norway|occupied Norway]] after April 1940) with a view to attacking Allied shipping [[convoy]]s, but Allied blocking efforts in the North Sea and in the GIUK gap impeded such break-outs. British forces [[British occupation of the Faroe Islands|occupied the Faroe Islands]] in April 1940, and [[Invasion of Iceland|Iceland]] in May 1940; the United States took over effective control of Greenland in 1940. But the German {{lang|de|[[Kriegsmarine]]}} profited greatly from the [[fall of France]] in June 1940, after which German submarines could operate from bases on the French coast.{{citation needed|date=July 2022}}

The origin of the term "gap" dates to this period, when there was a gap in air coverage known as the [[Mid-Atlantic gap]] or the "Greenland air gap". This gap was an area that land-based aircraft could not reach and where, as a result, they could not carry out their [[Anti-submarine warfare|anti-submarine]] duties.{{citation needed|date=July 2022}}

===Cold War===
The GIUK gap again became the focus of naval planning in the 1950s, as it represented the only available outlet into the Atlantic Ocean for Soviet submarines operating from their bases on the [[Kola Peninsula]].  NATO worried that if the Cold War "turned hot", naval convoys reinforcing Europe from the U.S. would suffer unacceptable losses if Soviet submarines could operate in the North Atlantic. The United States and Britain based much of their post-war naval strategy on blocking the gap, installing a chain of underwater listening posts right across it during the 1950s – an example of a [[SOSUS]] "sound surveillance system". This deployment of sonar surveillance in the gap, and elsewhere, hampered the Soviet Northern Fleet's ability to deploy its submarines without detection.<ref name="Sasgen 2009 p. 44">{{cite book |last=Sasgen |first=P. |url=https://archive.org/details/stalkingredbeart0000sasg |title=Stalking the Red Bear: The True Story of a U.S. Cold War Submarine's Covert Operations Against the Soviet Union |publisher=St. Martin's Press |year=2009 |isbn=978-1-4299-6697-9 |page=[https://archive.org/details/stalkingredbeart0000sasg/page/44 44] |access-date=13 March 2018 |url-access=registration}}</ref>

The Royal Navy's primary mission during the Cold War, excluding its nuclear deterrent role, involved anti-submarine warfare (ASW). The development of the {{sclass|Invincible|aircraft carrier|0}} ASW [[aircraft carrier]]s stemmed from this doctrine: their primary mission involved anti-submarine warfare using [[Westland Sea King|Sea King]] helicopters. The [[Type 23 frigate]] originated as a pure ASW platform; its mission expanded following the [[Falklands War]] of 1982.{{citation needed|date=August 2020}}

The largest Russian submarine drills through the GIUK gap were operations Aport and Atrina, in 1985 and 1987, respectively, when the Soviets deployed several SSNs near the U.S. coast before the [[Geneva Summit (1985)|1985 Gorbachev–Reagan meeting]].<ref>{{cite web |date=7 January 2007 |title=Операции "Апорт" и "Атрина" |url=https://podlodka.info/history/66-feat-submariners/638-operations-aport.html |url-status=dead |archive-url=https://web.archive.org/web/20210507170229/https://podlodka.info/history/66-feat-submariners/638-operations-aport.html |archive-date=7 May 2021 |access-date=9 November 2019 |website=podlodka.info}}</ref>

The Soviets planned to use the GIUK gap to intercept any NATO ships, especially aircraft carriers, heading towards the Soviet Union. Ships and submarines as well as [[Tupolev Tu-142]] maritime-surveillance aircraft aimed to track any threatening ships.{{citation needed|date=August 2020}}

The advent of longer-ranged Soviet [[submarine-launched ballistic missile]]s (SLBMs) allowed the Soviet Navy to deploy their [[ballistic missile submarine]] (SSBNs) within protected bastions in the [[Barents Sea]] and reduced their need to transit the GIUK gap. The much reduced, post-Cold War Russian Navy has even less need to transit the GIUK gap.{{citation needed|date=August 2020}}

Crossing the GIUK gap was a major strategic move for Ocean Venture in 1992, in which 84 NATO ships, including 4 US aircraft carriers, departed from their usual August exercise pattern, deployed a decoy south toward the mid-Atlantic, and then entered waters in a move that had historically been associated with a risk of destabilizing [[détente]].<ref>{{Citation |title=CSF 2017 {{!}} John F. Lehman: The Role of U.S. Naval War College in Resolving Conflict |date=7 August 2017 |url=https://www.youtube.com/watch?v=0uFi5Csqajk |access-date=26 November 2018 |publisher=U.S. Naval War College |via=YouTube}}</ref><ref>{{Cite journal |last=Barrett |first=Sharon |date=June 1993 |title=Ocean Venture 92: An Assessment of a Maritime Prepositioning Force/Joint Logistics Over the Shore Instream Offload Exercise |url=https://apps.dtic.mil/dtic/tr/fulltext/u2/a269713.pdf |url-status=live |journal=Naval Postgraduate SchoolThesis |archive-url=https://web.archive.org/web/20200801155513/https://apps.dtic.mil/dtic/tr/fulltext/u2/a269713.pdf |archive-date=1 August 2020}}</ref>

===Post-Cold War===
In late October 2019, a week before Commander of the Northern Fleet [[Aleksandr Alekseyevich Moiseyev|Aleksandr Moiseyev]] and Russian Foreign Minister [[Sergey Lavrov]] met their Norwegian counterparts in [[Kirkenes]], Norway, ten submarines of Russia's Northern Fleet, among them two diesel-electric and eight non-strategic nuclear, left their homebases in the Kola Peninsula to participate in submarine drills that were the largest, on the Russian side, since Cold War operations{{when|date=July 2022}} Aport and Atrina.{{clarify|what are "Aport" and "Atrina"?|date=July 2022}}
The main task of the submarines was reportedly testing Russian ability to breach the GIUK gap undetected and sail into the Atlantic Ocean. The drills were expected to last up to two months.<ref>{{cite web |date=29 October 2019 |title=Russian subs honing stealth skills in major North Atlantic drill, says |url=https://thebarentsobserver.com/en/security/2019/10/russian-northern-fleet-massive-submarine-show#.XbhEYg9Zr7I.twitter |access-date=9 November 2019 |website=thebarentsobserver.com}}</ref><ref>{{cite web |date=29 October 2019 |title=Russia Sends Ten Subs Into North Atlantic In Drill Unprecedented In Size Since Cold War |url=https://www.thedrive.com/the-war-zone/30728/russia-sends-ten-subs-into-north-atlantic-in-drill-unprecedented-in-size-since-cold-war |access-date=9 November 2019 |website=thedrive.com}}</ref>
== Significance to Denmark ==
Comprising [[Greenland]], the [[Faroe Islands]] and [[Denmark]], the [[Danish Realm|Kingdom of Denmark]] is an Arctic state alongside seven other countries whose territories cover the [[Arctic]] region.<ref>{{Cite web |title=The Arctic Council |url=https://www.arctic-council.org/ |access-date=2023-05-04 |website=Arctic Council |language=en}}</ref> All matters of foreign policy for both Greenland and the [[Faroe Islands]] fall within the jurisdiction of the Danish government.<ref>{{Cite web |title=Rigsfællesskabet |url=https://www.stm.dk/statsministeriet/rigsfaellesskabet/ |access-date=2023-05-04 |website=Statsministeriet |language=da}}</ref>

The Danish government has historically used its jurisdiction over foreign policy in both Greenland and the Faroe Islands to assist in securing the GIUK gap and the wider Arctic for its allies. In doing so, Denmark has arguably acquired a sense of goodwill from particularly the US government and [[NATO]].<ref name=":1">[https://cms.polsci.ku.dk/publikationer/groenlandskortet/ Henriksen, A. & Rahbek-Clemmensen, J. (2017), ''Grønlandskortet: Arktis’ betydning for Danmarks indflydelse i USA'', Centre for Military Studies, Copenhagen University]</ref> The Danish government views the Arctic as a central component of its foreign security policy and will continue to expand its spending, surveillance and military presence in the region.<ref name=":0">{{Cite web |title=Udenrigs- og Sikkerhedspolitisk Strategi 2022 |url=https://um.dk/udenrigspolitik/aktuelle-emner/udenrigs-og-sikkerhedspolitisk-strategi-2022 |access-date=2023-05-04 |website=Udenrigsministeriet |language=da}}</ref>

Despite the relatively small-sized population of Denmark, roughly 6 million, the Danish government's close ties to Greenland and the Faroe Islands legitimises it as an inherently important Arctic actor on matters of geopolitical security and great-power tensions. Danish assertion of sovereignty in the GIUK gap and the wider Arctic is already a key concern to the Danish Realm<ref>{{Cite journal |last=Choi |first=Tim |date=2020 |title=Not for Sale: Trump, Greenland and Danish Naval Diplomacy |journal=Canadian Naval Review |volume=15 |issue=3 |pages=2–4}}</ref> and is expected to be an increasingly important component of Denmark's future responsibilities in NATO.<ref>[https://cms.polsci.ku.dk/publikationer/efter-freden/ Kristensen, K. S. & Byrjalsen, N., (2022), ''Efter Freden: Ukrainekrigens betydning for dansk og europæisk sikkerhed'', Centre for Military Studies, Copenhagen University]</ref>

The GIUK gap is also a key supply line between the US and its European allies. With war on-going in Ukraine, NATO and the US are showing renewed interest in the GIUK gap,<ref name=":0" /> positioning Denmark to be a key player in matters of broader European security and increasing the gap's strategic importance to the Danish Realm.

=== Securing air and sea visibility in the GIUK gap ===
Until 2007, the Faroe Islands were home to an air surveillance radar station, providing vital radar coverage during the [[Cold War]].<ref name=":2">{{Cite web |title=Gauging the Gap: The Greenland–Iceland–United Kingdom Gap – A Strategic Assessment |url=https://www.iiss.org/research-paper/2022/05/gauging-the-gap-the-greenland-iceland-united-kingdom-gap-a-strategic-assessment/ |access-date=2023-05-04 |website=IISS |language=en}}</ref> In light of broader geopolitical changes, such as the [[Russian invasion of Ukraine]], {{circa}} 2022, the station was undergoing preparations to be reopened, closing an important surveillance gap in the GIUK gap.<ref>{{Cite web |last=Ritzau/The Local |date=June 9, 2022 |title=Denmark to 'close surveillance gap' with new Faroe Islands radar |url=https://www.thelocal.dk/20220609/denmark-to-close-surveillance-gap-with-new-faroe-islands-radar |access-date= |website=The Local}}</ref>

Maintaining thorough surveillance of the GIUK gap is crucial in order to ensure that [[Sea lines of communication|sea lines of communication (SLOCs)]] and supply lines are uninterrupted between NATO's European members and the United States. Military bases, space bases, surveillance drones and radar installations in both Greenland and the Faroe Islands can help ensure proper visibility in the region, and assist in [[Anti-submarine warfare|anti-submarine warfare (ASW)]] in case of actual conflict.<ref name=":1" /><ref name=":2" /><ref>{{Cite web |title=Søværnets nye fregatter |url=https://www.forsvaret.dk/da/nyheder/2020/sovarnets-nye-fregatter/ |access-date=2023-05-04 |website=Forsvaret |language=da}}</ref> In 2021, Denmark unveiled a $250 million investment in surveillance capabilities in Greenland and the Faroe Islands.<ref>{{Cite news |date=2021-02-14 |title=Denmark raises investment in Arctic surveillance to counter Russian build-up |work=Financial Times |url=https://www.ft.com/content/009f4c48-732d-4730-b396-f996588ca845 |access-date=2023-05-04}}</ref>

Responding to requests from NATO for Denmark to play its part in securing Arctic waters, Denmark is taking further steps to equip its ASW-frigates with sonar equipment, making them better equipped to detect and track submarines in the [[Arctic Ocean]], and particularly in the GIUK gap. In addition, the Danish government is equipping its Seahawk helicopters with sonar equipment and torpedoes. The upgrades have yet to be delivered, however, with delivery projections estimating 2024 at the earliest.<ref>{{Cite web |last=Pilgaard |first=Ronja |date=2023-05-02 |title=Forsvaret har taget to små skridt i retning af at kunne bekæmpe ubåde |url=https://www.berlingske.dk/content/item/1723099 |access-date=2023-05-04 |website=Berlingske.dk |language=da}}</ref>

=== Threats to critical seabed infrastructure ===
During the Cold War, Russia relied on the ability of its nuclear submarines to pass through the GIUK gap in order to ensure maximum military capability. The introduction of long-range precision strike weapons, however, have reduced the significance of the GIUK gap in relation to intercontinental attacks and made it possible for Russia to target North American sites from safer waters, such as the [[Norwegian Sea]]. Still, the GIUK gap remains the obvious access point for Russian military operations in the wider North [[Atlantic Ocean]] since most of Russia's highest quality naval capabilities are deployed in the [[Northern Fleet|Northern fleet]], making the GIUK gap a significant transit route.<ref name=":3">{{Cite web |title=The GIUK Gap's strategic significance |url=https://www.iiss.org/publications/strategic-comments/2019/the-giuk-gaps-strategic-significance/ |access-date=2023-05-04 |website=IISS |language=en}}</ref>

For NATO allies, the GIUK gap is vital in terms of barrier defense for sea lines of communication protection. [[Sea lines of communication|SLOCs]] are vulnerable in the North Atlantic both in the gap and beyond, and the US and NATO rely on Denmark to assist in protecting this critical infrastructure, including the vast number of seabed data cables.<ref name=":3" /><ref>{{Cite web |date=2022-08-17 |title=Forsvarsanalytiker: Dansk forsvar står ved en skillevej, og det kommende forsvarsforlig bliver afgørende |url=https://www.altinget.dk/forsvar/artikel/forsvarsanalytiker-dansk-forsvar-staar-ved-en-skillevej-og-det-kommende-forsvarsforlig-bliver-afgoerende |access-date=2023-05-04 |website=Forsvar}}</ref><ref>{{Cite web |date=2023-05-04 |title=Politikere vil have bedre bevogtning i vores farvande: 'Beredskabet på havet er ikke godt nok' |url=https://www.dr.dk/nyheder/indland/moerklagt/politikere-vil-have-bedre-bevogtning-i-vores-farvande-beredskabet-paa |access-date=2023-05-05 |website=DR |language=da-DK}}</ref>

The Russian fleet has in recent years strategically upgraded its capabilities for covert subsea operations related to the targeting of seabed infrastructure<ref name=":3" /> and reports of Russian "mapping" of critical seabed infrastructure in the North Sea and the seabed around Denmark are increasing.<ref>{{Cite web |date=2023-02-20 |title=Russia 'mapping' critical energy infrastructure, say Dutch intelligence agencies |url=https://www.politico.eu/article/russia-mapping-critical-energy-infrastructure-say-dutch-intelligence-agencies/ |access-date=2023-05-04 |website=POLITICO |language=en}}</ref><ref>{{Cite web |last=Larsen |first=Morten Soendergaard |title=Russian 'Ghost Ships' Are Turning the Seabed Into a Future Battlefield |url=https://foreignpolicy.com/2023/05/02/russia-europe-denmark-spy-surveillance-ships-seabed-cables/ |access-date=2023-05-04 |website=Foreign Policy |language=en-US}}</ref> NATO intelligence and security officials  confirm these reports, warning that Russia has both the intent and necessary capabilities to target critical seabed installations if they so choose.<ref>{{Cite web |date=2023-05-03 |title=NATO warns Russia could target undersea pipelines and cables |url=https://www.politico.eu/article/nato-warns-russia-could-target-undersea-pipelines-and-cables/ |access-date=2023-05-05 |website=POLITICO |language=en}}</ref> While such infrastructure has always been associated with some risk, the dependency of [[Denmark]] and its allies on them are only increasing and is therefore posing a major threat in times of tension short of actual conflict.<ref name=":2" />

==Significance to the United Kingdom==
{{See also|Armed forces of Scotland#GIUK gap}}
The GIUK gap is particularly important to the [[Royal Navy|UK's Royal Navy]], as any attempt by northern European forces to break into the open Atlantic would have to be made either through the heavily defended [[English Channel]], one of the world's busiest seaways,<ref>{{cite web |year=2007 |title=The Dover Strait |url=http://www.mcga.gov.uk/c4mca/mcga07-home/emergencyresponse/mcga-searchandrescue/mcga-hmcgsar-sarsystem/channel_navigation_information_service__cnis_/the_dover_strait.htm |url-status=dead |archive-url=https://web.archive.org/web/20100831173118/http://www.mcga.gov.uk/c4mca/mcga07-home/emergencyresponse/mcga-searchandrescue/mcga-hmcgsar-sarsystem/channel_navigation_information_service__cnis_/the_dover_strait.htm |archive-date=31 August 2010 |access-date=17 April 2010 |publisher=[[Maritime and Coastguard Agency]]}}</ref> or through one of the exits on either side of Iceland. As the British also control the strategic port of [[Gibraltar]] at the entrance to the [[Mediterranean]], this means Spain, France, and Portugal are the only Continental European countries that possess direct access to the Atlantic Ocean that cannot easily be blocked at a choke point by the Royal Navy.

==Bird migration==
The GIUK gap is also a route for [[bird migration|migratory bird]]s such as the [[northern wheatear]] to cross the Atlantic to reach Greenland and eastern Canada.

==In popular culture==
* The 1960 British war film ''[[Sink the Bismarck!]]'' discusses the strategic importance of the GIUK gap during World War II naval operations in the Atlantic theatre, and depicts the [[Battle of the Denmark Strait]] between British and German forces. It is based on the novel ''[[The Last Nine Days of the Bismarck]]'' by [[C. S. Forester]].
* The GIUK line is mentioned in the film ''[[The Bedford Incident]]''.  
* In [[Tom Clancy]]'s first novel, ''[[The Hunt for Red October]]'', the line was used to detect Soviet submarines entering the North Atlantic in pursuit of the rogue [[Typhoon-class submarine]] ''Red October'', whose officers were defecting to the United States with clandestine stealth technology. The event causes significant political and military tension between the United States and the [[Soviet Union]]. The [[The Hunt for Red October (film)|film adaptation]] also references the gap, with [[National Security Advisor (United States)|National Security Advisor]] Jeffrey Pelt (played by [[Richard Jordan]]) saying to the Soviet ambassador "Your aircraft have dropped enough [[Sonobuoy|sonar buoys]] so that a man could walk from Greenland to Iceland to Scotland without getting his feet wet."
* In Clancy's second novel, ''[[Red Storm Rising]]'', the line is featured more prominently after a war breaks out between [[NATO]] and the [[Warsaw Pact]]. The [[Soviet Union]] launches a surprise attack on the NATO airbase [[NAS Keflavik]] and invades Iceland. This causes the line to be destroyed, creating a gap in NATO's surveillance and allowing the [[Soviet Navy]] to enter the North Atlantic. The subsequent Soviet submarine attacks and air raids cause serious damage to [[US Merchant Marine|Merchant Marine]] ships and naval vessels in [[Exercise Reforger|Atlantic convoys]], hindering NATO's war effort during the defense against the less-successful Soviet invasion of West Germany.
* Early editions of the ''[[Harpoon (computer game)|Harpoon]]'' naval warfare simulation were based around defending the GIUK Gap. Tom Clancy used the simulation to test the naval battles for ''[[Red Storm Rising]]''.<ref>{{cite web|url=http://www.computerharpoon.com/hce|title=Harpoon Naval Warfare Simulation Game – AGSI – Harpoon Commanders Edition (HCE)}}{{dead link|date=October 2017 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>
* The location of Iceland in the gap made it a participant in the Cold War and a target for a nuclear strike, especially through the introduction of the aforementioned Keflavik atomic bomber NATO base. [[Halldór Laxness]] dramatized the tension of these geopolitics from the perspective of an Icelandic maid in the novel ''[[The Atom Station]]''.

==See also==
{{Commons category|GIUK gap}}
* {{annotated link|Battle of the Denmark Strait}}
* {{annotated link|Broad Fourteens}}
* {{annotated link|Communication with submarines}}
* {{annotated link|Long Forties}}
* {{annotated link|Mid-Atlantic gap}}
* {{annotated link|SOSUS}}
* {{annotated link|Western Approaches}}
* {{annotated link|Luzon Strait}}
* {{annotated link|Strait of Malacca}}
* {{annotated link|Strait of Gibraltar}}
* {{annotated link|Turkish straits}}

'''Land:'''
* {{annotated link|Focșani Gate}}
* {{annotated link|Fulda Gap}}
* {{annotated link|Suwałki Gap}}

==References==
{{Reflist}}

{{Soviet Union–United States relations|state=collapsed}}

[[Category:Atlantic Ocean]]
[[Category:Battle of the Atlantic]]
[[Category:Naval warfare]]
[[Category:Soviet Union–United Kingdom relations]]
[[Category:Iceland–United Kingdom relations]]
[[Category:Soviet Union–United States relations]]
[[Category:Military operations involving the Warsaw Pact]]
[[Category:NATO]]
[[Category:History of the Royal Navy]]
[[Category:Naval history of Canada]]
[[Category:History of the French Navy]]
[[Category:Naval history of Germany]]
[[Category:Naval history of the Netherlands]]
[[Category:History of the United States Navy]]
[[Category:Spanish Navy]]
[[Category:Portuguese Navy]]
[[Category:Soviet Navy]]
[[Category:Cold War in popular culture]]