If the Kerch bridges do come down, Crimea will be isolated at the end of a long, vulnerable supply line

TOM SHARPE 22 July 2024 •

Last week, the last remaining warship – a Project 1135 class patrol frigate – slunk quietly out of Sevastopol harbour, which had been the main base of Russia’s Black Sea Fleet since 2014. Ukrainian Navy spokesperson Dmytro Pletenchuk suggested we should “remember this day.”

I have cautioned previously about drawing too much hope overall from maritime success in this conflict, but what does this embarrassing withdrawal mean more widely? Operationally, the loss of the port is significant although it has been a long time coming. But is the scale of the embarrassment sufficient to have a strategic effect?

From a pure maritime perspective, this is the last in a long list of humiliations suffered by the Black Sea Fleet since the 2022 invasion.

April 2022 saw the sinking of the Fleet’s flagship, the cruiser Moskva. This was the first public indication that Russian warships’ ability to defend against even basic attacks was largely absent.

October that year saw the first multiple unmanned attacks with both air and sea drones surging into Sevastopol and damaging the corvette Admiral Makarov.

September 2023 saw a complex Storm Shadow missile attack, which crippled the warship Minsk and the submarine Rostov on Don, as well as hitting the Sevastopol naval headquarters building. These strikes were enabled by special forces and missile strikes on Russian S-400 air defence systems. Russian naval leadership retreated a few miles to their backup command post at Verkhne Sadovoe only for that to be hit in turn a few days later.  

At roughly the same time the Storm Shadows were wreaking havoc in Sevastopol, three Uncrewed Surface Vessels (USVs) were targeting the tanker Yaz and the arms ship Ursa Major. 

In October the then UK Armed Forces Minister James Heappey described the Black Sea Fleet as ‘functionally defeated’. I felt this was slightly premature for two reasons. First, at this point, Russian attempts to restrict the outflow of grain and other exports through the Bosphorus were still working. Second, Russia still had ships and submarines operating and armed with the Kalibr missile. This is a powerful cruise weapon with the legs to cover the whole of the Black Sea, no matter how far east Russia might have to retreat. One must remember that to target a ship with a Kalibr you need to know where it is and where it’s going – knowledge which the Russians were now finding hard to obtain in the western Black Sea. Putin’s men were limping but the Black Sea remained contested.

By December, however, the cumulative effect of all these strikes – and the fact that Russia was unable to spare proper surveillance aircraft for the Black Sea – meant that the waters between Odesa and Snake Island were safe enough for grain vessels and other merchant traffic. Cargoes could move reasonably safely between Ukrainian-held harbours and the territorial waters of Nato allies Romania, Bulgaria and Turkey, where the Russians dared not interfere with them. 

By March of this year, surface strikes using the Magura V5 Uncrewed Surface Vessel (USV) were in full swing and now, one third of the Black Sea Fleet fleet had been sunk. This caused the UK MoD to relabel the Fleet as “functionally inactive”, a more accurate description than “functionally defeated”, perhaps.

May saw a multi-pronged attack on the port of Novorossiysk, the Tuapse refinery and nearby oil terminal. This was by air and surface drones which defeated Russian defence systems and tactics once again. And then a few days later, American supplied Army Tactical Missile System (ATACMS) ballistic weapons struck the pier in Sevastopol, sinking the minesweeper Kurovets and hitting a Karakurt class Kalibr corvette – two of the few Russian warships which hadn’t fled Crimea for the relative safety of Novorossiysk. 

In the middle of all this, two attempts have been made on the Kerch road and rail bridges, one by a truck full of explosives and one by USVs. Both resulted in damage and repair bills but neither were decisive. The importance of the bridge, both tactically and symbolically makes it a valid ATACMS target and I have suggested in these pages that another attempt on it is only a matter of time. It remains unclear whether America has supplied ATACMS with potentially bridge-busting unitary warheads, as opposed to ones which deliver a spread of cluster submunitions – the latter type would be far less effective against major structures.

First is the impact the maritime attrition is having on Russia’s ability to fight at sea, blockade trade and ensure their own sea-based logistics. These are as close to zero as it’s possible to be, even with some Kalibr shooters still available. There may well be launchers and ships, but there probably aren’t many actual Kalibrs left to put in them: and Russia has basically no ability any more to locate and track targets across much of the Black Sea, meaning that Kalibrs can’t be used even if they are available.

Russia’s inability to move supplies by sea is probably not a major factor along the eastern part of the battle front, but at the western end of the front lines all supplies must now come either across the Kerch bridges or all the way from the 2014 Russian border, across the land bridge which is now entirely within the ATACMS envelope. If the bridges do come down, Russian troops on the Dnipro and in Crimea will have no credible avenue of retreat and will be at the end of long, vulnerable supply lines.

So the second major point is the status of Crimea itself. This totemic peninsula, described by Putin as Russia’s ‘holy land’ is already no longer a viable base for maritime operations. There is at least the possibility that Putin will come – perhaps has already come – to find it a burden rather than a military asset. The Kerch bridges are within range of ATACMS, Storm Shadow/SCALP and both the Stalker and Magura USVs. Ukraine has shown repeatedly that it has the capability to combine these weapons to great effect.

If Crimea does get cut off and its garrison – perhaps also the civilians remaining there – are starved out, what does that do to the whole war? Losing Sevastopol is one thing, is losing the ‘holy land’ strategically and politically sustainable for Putin?

This leads me to the third and perhaps most important point, one of escalation management. Arguably it has been the fear of crossing Putin’s red lines that has determined the pace and nature of response from Nato and other allies. The US, in particular, has been accused of over-caution in this regard, with Britain and France left to lead the way in supplying battle tanks and long-ranging missiles.

Does this metric now shift as a result of Sevastopol? How many more red lines need to be crossed without response before President Biden and his team feel they can up the ante? Some movement must be happening in Washington. Will it be enough for support levels to become decisive? Too soon to tell, perhaps, but one to watch. 

Lifting our focus for a moment from the Black Sea, it has to be said that it is not only Putin who has allowed his enemies to cross red lines and done nothing. The West has been guilty of this too. Syria in 2013 is an obvious example but more recently, endless Russian and Chinese activity at sea has been conducted in a grey zone where proportional and legal responses are hard to come by. By quietly crossing Putin’s red lines, President Zelensky and his Western backers are finally pushing back.

Being driven out of your premier naval base in the only active theatre of war is embarrassing, but the operational implications are probably less significant than the strategic effects on escalation management, Nato support levels and Ukrainian fighting morale.

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Tom Sharpe is a former Royal Navy officer and a graduate of the UK armed forces’ Advanced Command and Staff Course