The GIUK gap – The chokepoint in Britain’s backyard

Although the GIUK Gap has become a strategic symbol of NATO’s efforts to contain the Soviet Union at sea, the Gap has an intertwined history and long-standing influence over British strategic thinking.

The Soviet Union and its main successor, the Russian Federation, are only the latest competitors that constantly remind the governments in London of the relevance of maintaining relative control of its maritime backyard.

The open waters of the Northern Atlantic Ocean between the landmasses of Greenland, Iceland, and the United Kingdom form the so-called “GIUK Gap”, a naval chokepoint that historically bears a particular relevance for the UK’s strategic approach to continental powers of Europe, particularly in regards to Germany and Russia. During the Cold War, the North Atlantic Treaty Organisation (NATO) put the gap at the centre of its submarine strategy against Soviet incursions into the Atlantic. For the UK, the relevance of the GIUK Gap went beyond containing the Soviets.

Historically, “minding the Gap” was essential for any British attempt to establish an effective blockade against the majority of the land powers in northern Europe. Britain’s geographic position, naval primacy, and control of Gibraltar at the entrance of the Mediterranean Sea granted that only France, Spain and Portugal could not be easily blocked at a naval chokepoint by the Royal Navy. During the Cold War, Turkish membership of NATO secured that the organisation had control over an additional strategic area – the Dardanelles and the Bosphorus Strait – aimed at containing the Soviet Union outside the warm Mediterranean waters.

In the first half of the twentieth century, the area currently known as the GIUK Gap grew in relevance as the First World War unfolded. Although Imperial Germany could not achieve naval supremacy or significantly cripple the Royal Navy, the commerce raiders of the Kaiserliche Marine could attempt to break from the British blockade through the northern waters between the British Isles, Iceland and Greenland. Decades later, during the Second World War, the gap became widely used by military vessels of Nazi Germany.

The threat posed by the Kriegsmarine’s submarine force against the sea lanes that sustained the British war effort grew after the German conquest of Denmark and Norway in April 1940. The latter, in particular, had some of its naval facilities in the North Sea redesigned or built to serve the Kriegsmarine. A few days after the fall of Denmark, Britain reacted by occupying the Faroe Islands, a part of Denmark that Germany did not take. Meanwhile, Greenland’s officials sent a request for protection to the United States, which the American Administration accepted.

British Government occupied Iceland to secure the GIUK Gap, despite the fall of France providing a new option for Germany

Following increasing worries about Iceland’s neutrality and the possibility of German submarines using Reykjavík’s harbours, the British Government elaborated an operation to occupy the country, eliminating the enormous strategic risk that a German-controlled Iceland could present to the Allied war effort. In May 1940, Operation Fork resulted in the British occupation of Iceland. Thus, displaying the strategic relevance of the region, within two weeks after the fall of Denmark and Norway, the UK and the United States secured the remaining components of the GIUK Gap: Iceland and Greenland.

The fall of France in June 1940 gave Germany a new option of access to the Atlantic Ocean. Despite that, the northern routes remained crucial in the war at sea. An example of the Gap’s usage by the Germans is the short escape into the Northern Atlantic Ocean by the battleship Bismarck and the heavy cruiser Prinz Eugen in late May 1941. The naval engagement between the two vessels of the Kriegsmarine and the Royal Navy, resulting in the sinking of the already battlecruiser HMS Hood, became known as the Battle of the Denmark Strait and occurred near the GIUK Gap.

In the following three days, the resources spent by the British Government to sink the Bismarck demonstrated how the loss of the mighty Hood had affected the Government in London. Additionally, and most importantly, German military vessels could not venture into the Atlantic and threaten British supply lanes and other assets without fierce opposition. Therefore, the order to “sink the Bismarck” is also directly tied to the British insecurities of a scenario where the Kriegsmarine could not be contained within the natural boundaries of the Gap.

During Cold War, GIUK Gap’s strategic importance grew for NATO to monitor Soviet presence and prevent Atlantic access

During the Cold War, the GIUK Gap’s relevance only grew. Besides the traditional centrality to Britain, most of the NATO members recognised the strategic importance of the Gap in its Northern Flank. For NATO, the GIUK Gap involved two main issues: monitoring the Soviet presence in the area and, if the Cold War turned “hot”, preventing the Soviets from breaking into the Atlantic. In short, any attempt at a naval blockade on the Soviet Union required control over the Gap. According to Nick Childs, Senior Fellow for Naval Forces and Maritime Security of the International Institute for Strategic Studies (IISS), the Northern Flank was a “theatre that came to be seen by both sides as second only in importance to the European Central Front”.

In the 1950s, concerns about the increasing Soviet fleet of submarines and new surface vessels designed for the North Atlantic reinforced the perception that the GIUK Gap would play a crucial role throughout the Cold War. Throughout the 1950s, the United States implemented a passive sonar system (Sound Surveillance System, known as SOSUS) that could track Soviet submarines approaching the GIUK gap. As other new systems were delivered, including Surveillance Towed Array Sensors, the SOSUS became in the mid-1980s the Integrated Undersea Surveillance System (IUSS).

In the early years of the Cold War, NATO’s naval strategy for its Northern Flank consisted of putting Moscow in a defensive position. This strategy was based on the assumption to take the war to the “source” of the Soviet naval power, beyond the Norwegian Sea, more specifically on the Kola Peninsula. Aircraft carriers would play a vital role in these early plans. Nick Childs notes the nuclear dynamics of the region, for in the first years of the ballistic-missile submarines, the technology allowed only a strike range that demanded Soviet submarines to break into the Atlantic through the GIUK gap to be able to threaten American targets.

GIUK Gap remained strategically relevant during Cold War for Soviet naval push in Northern Atlantic, with NATO shifting between offensive and defensive stance

Even the more capable Yankee-class submarines armed with the RS-SS-N-6 Serb missile had to cross the Gap until the new generation of weapons in the 1970s could end that need. However, even with the advent of new and more advanced weapons in the 1970s and 1980s, the gap remained relevant due to the persistent risk of a Soviet naval push for the Northern Atlantic – seeking to eliminate NATO naval formations, for example.

From the 1960s to the end of the Cold War, the United States, Britain, and other NATO naval powers shifted back and forth their unified approach to the Soviet threat in the Northern Flank from an “offensive” stance – with plans to actively bring the war to the Norwegian and Barents seas if conflict broke-out – to a “defensive” position, which saw the GIUK gap as a barrier to contain the Soviet Navy outside of the Atlantic. In the 1980s, backed by new Anti-Submarine Warfare (ASW) capabilities and confidence in its technological lead, NATO returned to its offensive positioning, pressuring the Soviets to compete again with the West in the naval field or surrender the initiative within the area north of Norway.

Britain increasingly employed the Royal Navy as a service focused on anti-submarine warfare during this period. Unsurprisingly, by the early 1980s, the Royal Navy was a leading force in anti-submarine warfare. In this context, even assets that could be seen as a “power projection” or expeditionary platforms were designed to enhance the anti-submarine capabilities of the fleet at the expense of the expeditionary approach.

Having lessons from the World Wars, Britain had long recognised the GIUK Gap as the gateway between the northern European waters and the Atlantic and beyond. For the British, the Gap had an additional feature that reinforced the necessity of controlling this sea lane. In addition to the “blockade” that effective control of the GIUK Gap could impose on countries of Northern Europe, its geographic position meant that for Britain, the gap was within the immediate surroundings of the British Isles. In other words, the GIUK gap is part of the British “back yard” maintaining a military presence and surveillance was not a choice but a necessity.

Britain’s commitment to the GIUK Gap led to lack of long-term strategic thinking

Britain’s commitment to this area proved not to be without drawbacks for its position elsewhere. The Falklands War displayed strategic miscalculations within the British Government, which had been neglecting expeditionary capabilities since at least the late 1960s. As Lawrence Freedman argued, when the war in South Atlantic broke out, its expeditionary nature was precisely the kind of conflict Britain was the least prepared to wage. Nevertheless, it is worth noting that this issue is more a problem of lack of long-term strategic thinking – which generally occurs when a government allows the Treasury to dictate most of the Defence Policy – than an error of assessment by officers on the GIUK Gap’s relevance.

The lessons from the Falklands War influenced the retention of capabilities that otherwise would have been removed from service by the questionable 1981 Defence White Paper (also known as the Nott Defence Review). However, the end of the Cold War, less than a decade after the conflict in the South Atlantic, propelled the return of expeditionary forces to the centre stage of British strategic considerations. Attention shifted elsewhere after the end of the Soviet threat. Thus, in the 1990s, the GIUK Gap declined in relevance for Britain and other NATO allies.

The Soviet Union’s successor, the Russian Federation, had a fraction of the Soviet naval capabilities. Although the decline of Russian naval forces was severe, the reduction in military assets was not one-sided. The leading naval powers of NATO entered a period labelled “the Peace Dividend”, performing cuts and budget reassessments for the new strategic reality of the 1990s. Surface vessel numbers suffered as the Peace Dividend spread throughout the Alliance. In the mid-1980s, the navies of the US, the UK, France, Italy, Germany, Canada, Spain, and Norway had approximately 234 operational frigates.

One decade later, that number had fallen to 172; by the early 2010s, it dropped below 100 commissioned frigates. Over time, the decline of frigate numbers is a strong indicator of changing priorities and threat perceptions. More importantly, it signals a weakened overall ASW capability. It is worth noting that NATO’s leading military spenders increased the capabilities of its units since the mid-1980s. Still, the reduced numbers present questions when facing growing rivalry with other major powers.

The reduction of assets designed for ASW operations was in line with the motto of NATO in the 1990s: “out of area or out of business”. This rationale meant that expeditionary forces would be the priority of the Alliance’s major members. In Britain, attention and priorities gradually shifted from the Euro-North Atlantic area to include other regions, particularly the Middle East, including the Persian Gulf. In the years 2000 to early 2002, during the British intervention in Sierra Leone’s Civil War (1991-2002), the South Atlantic and Western Africa momentarily became the centre of Britain’s military efforts in the western hemisphere. The intervention vindicated once more the expeditionary concept, displaying the relevance of the retention of high-readiness capabilities.

Meanwhile, in 2001, Britain, as part of a coalition led by the United States, deployed forces to invade Afghanistan. Two years later, the invasion of Iraq occurred. In short, the late 1990s and early 2000s were marked by the consolidation of the expeditionary approach. Britain was one of the most enthusiastic countries to adopt the strategic reorganisation of its armed forces into an expeditionary model.

Since the mid-2000s, Russia’s reassessment of its capabilities and revisionist foreign policy led to increased concerns about the GIUK Gap

However, since the mid-2000s, the first signs indicating that the expeditionary or “out of area” vision should be combined with the traditional focus on ASW and high-intensity warfare – that characterised defence policies of NATO members during the Cold War – appeared as Russia began reassessing its capabilities and adopted a revisionist foreign policy. In 2014, Russia invaded Ukraine and annexed Crimea, leading to a new antagonism between Moscow and NATO. Initially, the Alliance’s response to Russian aggression against Ukraine concentrated on reassuring the Baltic and Central European member states, focusing on land and air warfare capabilities.

However, since 2014, NATO has acknowledged that its Enhanced Forward Presence strategy must be backed by a credible naval force sustaining the transatlantic reinforcement plans that would be triggered in case of open conflict. Moreover, Russia’s increased submarine capabilities and hybrid warfare tactics returned the GIUK Gap and ASW back to the centre stage of the naval strategic considerations in the European theatre.

Concerns about a new “Battle of the Atlantic” were among the reasons that led the United States to re-establishing its 2nd Fleet in 2018 after only seven years since it was deactivated. Pentagon spokesman Johnny Michael stated that “NATO is refocusing on the Atlantic in recognition of the great power competition prompted by a resurgent Russia”. That same year, a US Navy carrier was deployed into the Artic Circle for the first time in more than two decades.

Extended carrier deployments of the US Navy occurred in European waters for the first time in years, especially in the Northeast Atlantic. In 2018, the United States, aiming to base additional maritime patrol aircraft near the GIUK Gap, refurbished its facilities in Keflavík, Iceland.

Three years earlier, in 2015, Britain had published its then-newest Defence Review. The British Government had decided to partially amend the decisions of the previous 2010 Review, indicating that the age of budget cuts was over and leaving open the possibility of expanding the surface fleet of the Royal Navy. Nevertheless, the growing state-based threat displayed by Russia’s annexation of Ukraine did not result in significant changes in the fortunes of the Ministry of Defence and Armed Forces.

The 2015 Review is characterised as one attempt to mend unnecessary mistakes committed by its predecessor – the 2010 Review – while still avoiding adopting significant policies that would provide the amends to those strategic errors. Commitments included small increases for the Royal Navy (an additional 400 personnel) and Royal Air Force (300 personnel) and the maintenance of the 82,000-sized regular British Army backed by 35,000 reservists.

One of the highlights of the 2015 Strategic Defence Review is the decision to eliminate a capability gap left by the retirement of Hawker Siddeley Nimrod in 2011 and the scrapping of its planned successor, the Nimrod MRA4. The British-built and developed Nimrod was a maritime patrol aircraft designed mainly for ASW operations. Nimrod’s secondary roles included maritime surveillance and anti-surface warfare (ASuW). In other words, the capabilities offered by the Nimrod were central in sustaining relative control of the GIUK Gap. Shortly before the British Government decided to retire the Nimrod without a successor, the National Audit Office that “the maintenance of the integrity of the UK through detection of hostile air and sea craft would be compromised” if those assets were retired and the successor programme cancelled. Despite the risk to national security, the British Government advanced with its plans and the Nimrod and its successor were scrapped and cancelled, respectively.

The lack of suitable aircraft left Britain with a new challenge when trying to detect Russian submarines, not only when they crossed the GIUK Gap but also in other areas. Another direct consequence of the Nimrod retirement was the strain on the Royal Navy’s frigates as they were expected to cover the gap left by the 2010 Defence Review. A display of that capability issue was seen in late 2014 through the joint deployment to RAF Lossiemouth of four French, American and Canadian maritime patrol aircraft to attempt to locate Russian submarines near the GIUK Gap. Following these events, the 2015 Review committed to purchasing nine Boeing P-8 Poseidon maritime patrol aircraft.

The first P-8 Poseidon arrived in the UK (Kinloss Barracks, Scotland) in February 2020 before relocating to RAF Lossiemouth in October 2020. Boeing delivered the last of the nine P-8 in January 2022. However, even though the P-8s are capable and modern assets, the capability provided by only nine Poseidons can be questioned, particularly for the UK’s geographic position and global ambitions. It is worth mentioning that Anglo-American cooperation with Norway, another P-8 operator, is underway. Cooperation with other nations is a way to counter criticism regarding the number of purchased aircraft while improving interoperability and expanding joint capabilities.

Since the renewed tension with Russia, Britain, the United States, and others recognised the threat posed by that possible enemy to NATO’s sea lines of communications. In this case, the UK’s stance is further complicated by its position as an insular nation. Additionally, a significant amount of the undersea cables of communication of continental Europe passes through the British Isles before linking with the United States (and vice-versa). Hence the relevance of the GIUK Gap for the security of the sea lines of communications above and underwater. Concomitantly, the Allied Maritime Command of NATO has reoriented its training towards ASW. The Allied Command’s objective is clear: rebuild high-end anti-submarine warfare (ASW) skills while supporting new defence policies centred on ASW. Support comes through the joint exercises gathering member states with high-level ASW skills alongside others attempting to rebuild or increase that capability.

In Britain, beyond the plans for expanding the size of the frigate fleet from 13 to 18 through the planned Type 32, a new question on the size of the submarine force is gaining ground within the ranks of the Ministry of Defence. In September 2022, the Defence Secretary asked the Royal Navy to study the balance between the surface fleet and submarines.

This decision follows the recommendation of the Defence Committee dating from February 2022, which stated the Government “should explore increasing the size of the of the attack submarine fleet as part of the Astute successor programme, Submersible Ship Nuclear Replacement (SSNR)”. Another issue raised by the Committee was “the availability of attack submarines and destroyers, and the lack of Fleet Solid Support shipping”. Within this context, Ben Wallace, Secretary of State for Defence, summed up the British position: “We’re planning on growing our surface fleet, but is our sub-sea fleet big enough?

If it isn’t, do we trade one off against the other [or] do we find money from elsewhere?”. These questions and concerns are the results of an increasingly unstable international system and several rounds of cuts performed without adequate reasoning and strategic planning. The international scene has changed significantly since the 2010 Defence Review. However, capabilities lost take time to recover.

Despite the possible parallels traced with the Cold War, the Russian Federation of the early 2020s is not on the same level that the Soviet Union was at its peak. In 2022, following the 2014 Annexation of Crimea, Russia attempted to duplicate the 2014 events by furthering the cause of a “Great Russia” – once again – at the expense of Ukraine. The outcome of the ongoing Russian-Ukrainian conflict remains open. Still, it is proving to be a series of disastrous displays for the Russian military and political prestige, exposing the fractures and structural problems that the military reforms of the late 2000s and 2010s did not solve.

Additionally, the eruption of violent confrontations derived from delicate long-standing disputes between countries regarded by Moscow as its spheres of influence has occurred since the invasion of Ukraine. The clashes between Kyrgyzstan and Tajikistan throughout 2022, culminating in confrontations from 14 September to 20 September 2022, can be pointed out as one example.

The perceived inaction of Russia in preventing the previous bloody border clashes between Armenia and Azerbaijan between 12–14 September 2022 might have led to the emboldening of the parties involved in the Kyrgyzstan-Tajikistan border dispute. These clashes were marked by the lack of Russian military involvement, while politically, the reassurances coming from Moscow did not please its partners caught by the renewed conflicts. In short, although Russia is a significant military power, its current position seems more delicate than Moscow desired when deciding on the offensive against its neighbour in Eastern Europe.

The GIUK Gap remains relevant as a chokepoint for the Russian Navy

However, as the war in Ukraine shows, NATO has to remain vigilant, and the era of the Peace Dividend is long over in Europe. According to the International Institute for Strategic Studies (IISS), the alleged potency of modern Russian submarines has increased significantly while Western advantages in relative detection ranges have narrowed. Concomitantly, the Alliance’s ASW has been suffering a direct consequence of the decline in the numbers of operational submarines and other ASW-oriented vessels: the “erosion of operator skills”.

Therefore, as the IISS argues, one of the changes since the Cold War era is that rather than focusing on large numbers of enemy submarines dashing across the GIUK Gap, the current scenario is marked by “small numbers of high-capability assets seeking a strategic advantage”.

Moreover, despite several challenges, Russia continues seeking a “blue-water” naval capacity, meaning that the GIUK Gap will remain relevant despite the growing capabilities of long-range precision strike weapons. Another point contributing to the continued relevance of NATO’s Northern Flank and GIUK Gap is the disposition of the Russian Navy.

Based on the Kola Peninsula, the Northern Fleet is the most capable Russian naval formation, bearing the assets considered the pride of the Navy, especially within the submarine force. Thus, the Gap remains a crucial chokepoint as long as the Russian Navy tries to venture outside the Barents and White seas. Nevertheless, environmental changes in the Arctic sea ice may alter that scenario. Even if new maritime routes were established after reductions in Arctic sea ice, enabling easier deployments to Asia, Russia would still need to cross the GIUK Gap to access the Atlantic easily.

In conclusion, growing tensions between the nations wielding great power have propelled the GIUK Gap back to centre stage. The Gap will remain an extremely relevant passage connecting most Northern Europe to the Atlantic and elsewhere. Competition in the area is also leading the Great Powers and their allies to seek the strengthening of ASW capabilities and skills. The technological advancements within the field have increased the deployment of autonomous and remote systems alongside the ever-more-capable modern submarines. For Britain, the Gap is part of its direct strategic surrounding, its prioritisation within Defence Policy is not an option but a necessity.

Reinforcing its relative control of the GIUK Gap does not need to lead to cuts elsewhere, for the lesson taken from the debate about the size of the submarine and frigate fleet – and the size of the Royal Navy as a whole – is clear: recovering capabilities is not as easy as giving them away.

The gap between material demands, Government statements, and actual forces can expose any nation to serious security threats, particularly countries that regard themselves as bearers of global interests and power.