Ukraine’s Sea Denial Strategy: Lessons for the Persian Gulf

For the first time, remotely operated “uncrewed” (or “unmanned”) systems played a decisive role at sea just as they did on land.  Ukraine, using uncrewed surface vessels (USVs), uncrewed aerial vehicles (UAVs), and cruise missiles, damaged or destroyed enough of Russia’s ships and shore-based infrastructure that the Russian Navy was forced to curtail operations in the western Black Sea and move its most critical assets to the eastern port of Novorossiysk. While the cruise missiles, UAVs, and USVs deserve much of the credit for Ukraine’s accomplishments, other factors such as geography, leadership, and constant tactical innovation also played major roles in Ukraine’s success.  And while there are important differences between the situations in the 2022 Black Sea and the 2026 Persian Gulf, Ukraine’s success in playing the cards it was dealt is a cautionary tale for US and allied planners considering expanding operations against Iran in the Strait of Hormuz.

Summary of Black Sea Battles: 2022-2025

In February 2022, Russia’s Black Sea Fleet (BSF) dwarfed the small Ukrainian Navy in both numbers and capability.  The BSF order of battle included a guided missile cruiser, multiple submarines and surface vessels capable of launching Russia’s Kalibr cruise missiles, amphibious landing craft, fixed and rotary wing aircraft, and coastal defense cruise missiles.  By contrast, Ukraine’s naval order of battle was quite small and most of its ships were obsolete. 

Figure 1. ChatGPT derived chart comparing available naval capabilities in the Black Sea at the outset of Russia’s invasion of Ukraine in February 2022, including Russian reinforcements from the Baltic and Northern Fleets. 

Although not public, it is possible now to infer the key elements of the BSF’s offensive strategy from its initial operations.  First, it planned  to conduct land-attack strikes deep into Ukraine to both damage Ukraine’s infrastructure and intimidate its people.  The BSF also wanted to quickly establish control over Ukraine’s littoral areas to facilitate Russian ground and amphibious operations along the coast and to institute a de facto blockade of Ukraine’s ports to strangle its economy.  From the outset, the Russian Navy sank or disabled several of Ukraine’s remaining  vessels (Ukraine scuttled others), began the land attack strikes, and conducted landings along the coast of the Sea of Azov to facilitate ground operations. The BSF also seized Snake Island, a tiny, rocky outcrop a little over 35 kilometers from the western Ukrainian coast that housed a small Ukrainian garrison. The BSF then began patrols in the northwest Black Sea to hold the island and control access to Ukraine’s vital ports at Odesa and on the Danube River.  Many of these operations were supported out of the Black Sea Fleet’s massive base at Sevastopol on the Crimean Peninsula. 

Almost from the start, despite the lack of major combatants, Ukraine was able to use a limited number of available weapons to make Russian operations in the northwest Black Sea very costly.  First, Ukraine reportedly sowed mines along its western coast to deter additional Russian landings.  Next, in April, Ukraine used a pair of cruise missiles to sink the Russian cruiser Moskva, the BSF’s flagship. Kyiv then used a combination of cruise missiles and armed UAVs to destroy additional vessels attempting to resupply Snake Island and to strike the Russian forces on the island itself.  These attacks made Russia’s ability to resupply of the island too costly and the Russians abandoned it in June of 2022.  The BSF also moved surface operations well out of cruise missile range in the northwestern Black Sea but continued to patrol there. The sinking of the Moskva and the return of Snake Island not only damaged Russian operational capabilities, but they also provided a needed boost to Ukrainian morale and validated the nascent strategy.

Next, Ukraine used a combination of USVs, UAVs, and long-range cruise missiles to damage or sink more Russian vessels at sea and in ports on the Crimean Peninsula. The campaign began in the west but eventually widened to include many other areas of the Black Sea. It  also included attacks on Russia’s essential Kerch Strait Bridge, the BSF base at Novorossiysk, and civilian tankers carrying Russian oil.  By mid-2024, the open source research group Oryx validated damage to or loss of 29 Russian naval vessels of all types, including one guided missile cruiser, two submarines, three corvettes, and seven amphibious landing craft.  These losses seemed to convince the BSF to adopt a more defensive posture, including curtailing operations in the western Black Sea, largely abandoning Sevastopol, and relocating many of remaining assets to Novorossiysk by early 2024.  These developments have not stopped BSF operations in the Black Sea, but have made it far more difficult for Russia to threaten the Ukrainian coast or to interdict commercial ship traffic along the coastal corridor between Ukraine’s western ports and the Bosphorus, a vital lifeline for Ukrainian commerce.  The BSF can still threaten deep strikes into Ukraine from the eastern and southern Black Sea given the range of its Kalibr cruise missiles, but has conducted fewer of these in recent months, probably due to a mix of technical reasons and the availability of cheaper munitions.    

Screengrab from video released by Ukraine’s Main Intelligence Directorate reportedly showing a Ukrainian uncrewed surface vessel (USV) strike against the Russian Bykov-class patrol ship Sergei Kotov in the Black Sea, March 2024. Full video available here.

The Geography Card

Despite its obvious disadvantages in traditional naval capacity, Ukraine brilliantly played several cards it held to achieve success in this “sea denial” campaign.  First, Ukraine was able to take advantage of favorable geography.  The Black Sea is relatively small by comparison to the world’s oceans, only about  1175 kilometersacross at its widest point (Map 1).  The Russian Navy’s strategy initially called for patrols mostly in the northern littoral zones, further condensing the area of operations.  This small space close to Ukrainian held territory facilitated the initial strikes against Russian ships using the cruise missiles, UAVs, and USVs.  As Ukraine’s strategy and tools grew more sophisticated, Crimea’s location, about 300 kilometers from Odesa, also made execution easier.  Ukraine was able to attack Sevastopol’s berthing areas and other Crimean shipyardsseveral times, damaging some vessels and increasing Russia’s fear for its remaining expensive assets.  Finally, large ships entering or exiting the Black Sea must transit the Turkish Straits, and Turkey closed the straits to most Russian and Ukrainian combatant vessels after the start of Russia’s 2022 invasion in accordance with the 1936 Montreux Convention.  This prevented the Russian Navy from reinforcing the BSF with all but very small vessels that it could deploy from other fleets via Russia’s internal river system, limiting its options for augmenting its naval power in the Black Sea. 

Map 1: The Black Sea. Source: Wikipedia

Iran probably has even more geographic advantages than Ukraine in its confrontation with the US and allied militaries. Access from the Persian Gulf to the open ocean passes through the Strait of Hormuz , a roughly 167 kilometer long waterway between Iran and Oman that ranges from about 39 and 97 kilometers in width (Map 2).  It is easily defended with minimal assets including mines, cruise missiles, fast attack boats, and USVs.  Iran controls seven islands in or near the strait and has fortified some of these, including with underground missile storage.  These islands are prime locations for sea denial operations against large capital ships using weapons like those used by Ukraine. 

In addition to the islands, Iran has multiple bases along its hundreds of kilometers of coastline that dominate both the eastern and western approaches to the strait and the strait itself.  The rugged terrain of these areas provide potential hiding places for missile systems and small USVs that can easily be moved up to the shoreline or into the water for “shoot and scoot” missions when needed. By late March, the US and Israel claim to have damaged most of Iran’s bases and many of its naval vessels in the area, but as Ukraine’s experience shows, very few Iranian strikes against expensive US warships or commercial tankers would be needed for a sea denial strategy to succeed. 

Of course, the US or its allies have ways they can attempt to counter such a denial campaign.  They can, for example, attempt to constantly monitor these islands and the Iranian coastline to interdict any small groups operating from those areas, but that will require large numbers of intelligence, surveillance, and reconnaissance assets and ready strike forces given the size of the region, a huge potential drain on available resources.  Another option would be to seize some of the islands or sections of the Iranian coast, but as Ukraine’s experience with Snake Island shows, holding an island close to an enemy coastline may prove difficult over time and costly in terms of lives and equipment.  The Allied attempt  to hold lodgments at Gallipolion the Turkish coast in 1915 provides another historical example of how costly this type of operation might be. 

Map 2: showing the political boundaries and shipping lanes of the Strait of Hormuz.  Source: Wikipedia

The Leadership Card

There is no question that Ukrainian leaders at all levels, from strategic to tactical, have outperformed their Russian counterparts throughout Russia’s campaign in Ukraine.  Historians will examine why the Ukrainians were successful for years.  In the Black Sea fight, Ukraine concentrated a significant portion of the planning and execution of its sea denial campaign in the hands of a small group from its intelligence community and the defense industry. According to Ukraine’s Snake Island Institute, this made the group less hierarchical and more autonomous, allowing it to test, deploy, and adapt USV systems very quickly.  The people in the group also mattered.  They were obviously dedicated professionals able to objectively evaluate the strengths and weaknesses of both the technology and tactics they were using, then quickly adapt as events progressed. 

By comparison, the Russian BSF’s leadership and staff were bigger and likely slowed by the Russian military’s highly centralized decision-making processes and staff inertia.  Existing perceptions also probably played a role as the Russians clearly dismissed the Ukrainians’ abilities to defend their territory from the start, leaving the BSF mentally unprepared for the innovative campaign that followed.  The Snake Island Institute’s analysisindicates the BSF was slow to adapt to Ukraine’s asymmetric operations, and when it did adapt, the Ukrainians quickly found ways to work around the Russian Navy’s new tactics. For example, the BSF learned to use aircraft patrols to try to identify and destroy Ukrainian USVs at sea and tried to jam USV signals.  The Ukrainians, in turn, modified their own tactics and technology, including arming USVs with anti-aircraft missile systems and redundant means of communication, complicating Russia’s ability to interdict them.    

Comparisons between the US military leadership and its Iranian counterparts are more difficult as the latest crisis is still in its early stages.  Over the last few months, the US military, along with its Israeli allies, have executed a brilliant campaign to destroy much of Iran’s conventional military capacity and decapitate Iranian leadership, suggesting US and Israeli military leaders have a deep understanding of their opponents and the Iranian environment.  In the maritime space, an Israeli strike killed a senior Iranian commander who played a key role in the development of the strategy and weapons Iran will need to control the Strait of Hormuz.  However, other analysts argue that Iran has built a “mosaic defense” in which personnel are united doctrinally and ideologically, but which also has a decentralized command structure with multiple layers and redundant capacity.  This allows independent operations to continue that adhere to the strategic intent of Iran’s leadership despite losses.  In fact, on March 27^th, an Iranian missile strike against a US airbase in Saudi Arabia reportedly destroyed or damaged a number of US aircraft, including a valuable E-3 Airborne Warning and Control System (AWACS), suggesting the remaining Iranian commanders know what to target and still have the means to do so. 

As Ukraine’s experience shows, a small group executing a sea denial strategy with asymmetric tools can achieve success despite numerical disadvantages. Such small groups don’t need a tremendous amount of hands-on leadership from the national level or internal hierarchy.  If they have local support and understand the strategic intent of their leadership, they only need a few successful operations to inflict casualties on their enemies and damage valuable assets. To counter such operations militarily could take vast resources and years of effort.  For example, the US military spent years hunting terrorist cells in Iraq and Syria after the 2003 invasion of Iraq and eventually achieved success.  However, it was a long fight with significant losses and financial cost, especially in the early years. The US could be setting itself up for another such campaign if it is not careful. 

The Technology Card

In the Black Sea fight, Ukraine clearly had (and still has) the technological means to execute its strategy.  Although it obtained some assets from foreign sources, many of the weapons successfully used against the Russian Navy were developed and built in Ukraine.  For example, the Neptune cruise missiles that sank the Russian cruiser Moskva were Ukrainian produced.  In addition, the USVs used to damage other Russian vessels were developed and produced in Ukraine at a cost of roughly $250,000 to $300,000 US dollars, far less than combatant ships.  More importantly, Ukrainian planners developed the tactics used in these strikes and adapted both the tactics and equipment as operations progressed.  Tactical innovations included combined USV and UAV strikes and swarming targets from multiple angles to confuse and overwhelm defenses.  The strategy did not call for massive numbers of these weapons; it used just enough to cause key losses in the Russian order of battle and convince the BSF to adopt a more defensive posture less threatening to Ukrainian interests.    

Iran reportedly has built an entire arsenal of weapons  it can use to make any attempt to forcibly access the Strait of Hormuz or seize Iranian territory quite costly, including many that Iran has produced on its own.  Iran, for example, developed the now infamous Shahed UAV that Russia has modified for operations against Ukraine.  Other Iranian weapons include anti-ship cruise missiles that can be launched from shore and thousands of mines that can be deployed from small boats.  News reports from early March indicate Iran has already begun to deploy the mines.  Iran also has a large fleet of fast attack boats intended to operate in swarms as well as USVs that Iranian forces reportedly used in two attacks against civilian oil tankers near Oman in early March.  These attacks and Iran’s additional warnings have caused maritime insurance costs for ships in the gulf to skyrocket and vastly decreased civilian traffic through the straits, validating Iran’s sea denial approach.  

Unlike their Russian counterparts in 2022, the US military clearly knows about potential Iranian maritime threats and have already taken steps to counter them.  For example, US forces claim to have destroyed 16 Iranian mine laying ships in early March along with multiple other Iranian vessels to preclude the deployment of mines.  The US bases ships equipped with mine countermeasures in the region as well.  The US has also deployed A-10 Thunderbolt II attack jets to the region to take on Iran’s fast attack boats and had some success in destroying them. Still, the Iranians can afford losses of these inexpensive assets and may not need a vast number of successes to achieve their goals.  As the Ukrainian experience shows, a few strikes by USVs at the waterline can badly damage or sink a modern warship.  Preventing those types of strikes will take extraordinary US and allied vigilance at all levels, particularly for ships at sea, a factor that could wear down crews over time. 

Conclusion

This paper is not intended to argue that Iran will succeed if more intense fighting between Iran and the US or other nations breaks out in the Strait of Hormuz, simply that Iran has cards it can play.  The Ukrainian example shows how a small group of dedicated personnel can use the geography of a constrained littoral area and a host of asymmetric tools to overcome vast conventional disadvantages to succeed against a more powerful foe.  Iran does not need many successful strikes in this type of strategy, and the low price of USVs and these other munitions make expending them in large quantities cost effective.  By contrast, the US Navy and its allies can’t suffer too many losses of expensive capital ships and aircraft that are already difficult to replace.  Highly trained naval personnel are also difficult to replace, particularly in war time.  The outcome remains to be seen. 

The US now claims that negotiations are underway to resolve the crisis, and the White House says opening the Strait of Hormuz will not necessarily be a condition for ending the war. Any result that leaves the status of the Strait of Hormuz unresolved could depress global commerce further and likely keep oil prices high. It would also validate Iran’s asymmetric strategy in this phase of the conflict. This, along with Ukraine’s success in the Black Sea, would demonstrate again that a small power can, in the right environment, design and execute a sea denial strategy against a much larger foe that does not require significant, and very expensive, conventional naval capability.  Only time will tell. 

Disclaimer: All statements of fact, opinion, or analysis expressed are those of the author and do not reflect the official positions or views of the US Government. Nothing in the contents should be construed as asserting or implying US Government authentication of information or endorsement of the author's views.