Sea of Azov

• 1. Introduction

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  The Sea of Azov holds a record that surprises almost everyone who hears it: it is the shallowest sea in the world. Its depth varies between 0.9 and 14 metres, shallower in many places than a backyard swimming pool. Connected to the Black Sea by the Strait of Kerch, which narrows to just 4 kilometres at its tightest point, this compact inland sea sits at the intersection of Eastern Europe, ancient trade, and modern conflict. It is 360 kilometres long and 180 kilometres wide, with an area of 39,000 square kilometres, and it has been coveted, fought over, and debated for thousands of years. How did a body of water this small become so consequential? What lives within its unusually fresh waters, and what has it cost so many nations to control it?

• 2. A Sea with Many Names

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  Ancient geographers knew the Sea of Azov as the Maeotis Swamp, a name drawn from the marshlands to its northeast. The strong river currents that flow into it misled classical observers so thoroughly that Herodotus, writing in the 5th century BC, judged it as large as the Black Sea itself. The Pseudo-Scylax, a century later, estimated it at roughly half that size. Neither was right. The fresh water pouring in from rivers led ancient writers to label it a swamp or a lake rather than a sea, an understandable error given its low salinity and unusual character.

  The name Azov itself likely traces back to the Kipchak Turkish word asak or azaq, meaning lowlands. One Russian tradition, however, offers a different origin story altogether: a Cuman prince named Azum or Asuf, said to have died defending his town in 1067. Medieval Russians called it the Sea of Surozh after the nearby city now known as Sudak. The Ottomans had their own name for it, Baluk-Denis, meaning Fish Sea, chosen to reflect the sea's legendary productivity. The Maeotians themselves, according to Pliny, called it Temarunda, meaning Mother of Waters. Polybius, writing in the 2nd century BC, confidently predicted that ongoing sediment deposits from rivers would eventually close the strait to the sea entirely. He was not entirely wrong about the direction of change.

• 3. The Shallows and Their Science

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  At an average depth of 7 metres, the Sea of Azov behaves less like an ocean sea and more like a vast, brackish lagoon. More than 20 rivers flow into it, but two of them, the Don and the Kuban, account for over 90 percent of the total water inflow. The Don contributes roughly twice as much as the Kuban. This constant freshwater input keeps salinity at 10-12 on the Practical Salinity Scale in the open sea, about one third of typical ocean salinity. In Taganrog Bay at the northeast end, salinity drops even further, to just 2-7 on the same scale.

  The shallowness has a striking consequence below the waterline. Oxygenated surface waters sit above an anoxic layer ranging from 0.5 to 4 metres thick. When organic matter from the active surface sinks to the bottom, bacteria exhaust all available oxygen consuming it, creating dead zones. Wind strength and sea surface temperature determine the exact boundary between the two layers. A stagnation zone lies between them. Meanwhile, the sea is slowly getting shallower: earlier hydrological expeditions recorded depths of up to 16 metres, but more recent surveys could find nowhere deeper than 13.5-14 metres.

  The Taman Peninsula, on the eastern shore, adds another geological dimension. It hosts about 25 mud volcanoes, most of them active. Their typical behaviour is quiet, oozing mud mixed with methane, carbon dioxide, and hydrogen sulfide. On the 6th of September 1799, near Golubitskaya stanitsa, one eruption lasted about 2 hours and threw up a mud island 100 metres in diameter and 2 metres high before the sea washed it away.

• 4. Extraordinary Biological Richness

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  The Ottoman name Fish Sea was not an exaggeration. The Sea of Azov was once the most productive fishing area in the Soviet Union, with typical annual catches of 300,000 tonnes, equivalent to 80 kilograms per hectare of surface. The comparable figure for the Black Sea was 2 kilograms per hectare; for the Mediterranean, just 0.5 kilograms. The sea's high biological output stems from its shallowness, which concentrates heat and sunlight, combined with the steady input of nutrients from the Don and Kuban rivers.

  More than 80 fish species and 300 invertebrate species have been identified here. Among them, 50 are listed as rare and 19 as endangered. The sturgeon Acipenser nudiventris is considered probably extinct in the region. The sea hosts around 600 species of planktonic algae, with diatoms and green algae dominating the count. It is green algae that give the water its characteristic colour visible in satellite images. Mollusks form between 60 and 98 percent of the invertebrate biomass on the sea floor.

  The shores and spits support dense bird colonies: wild geese, ducks, seagulls, cormorants, pelicans, swans, herons, and many birds of prey. One sub-species of harbour porpoise, Phocoena phocoena relicta, was once so closely associated with the sea that Soviet biologists simply called it the Azov dolphin. Today, dolphins are rarely observed here. Shallowing, pollution, navigation traffic, and collapsing fish populations have all pushed them out. The anchovy fisheries have collapsed entirely.

• 5. Peter I and the Fortress of Azov

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  In the spring of 1695, a Russian army of 31,000 men and 170 cannons arrived before Azov, a Turkish fortress on the sea's shore, garrisoned by 7,000 troops. Two assaults, on the 5th of August and the 25th of September, both failed. The siege was lifted and the army withdrew. Peter I had his first major setback.

  What came next was a winter of shipbuilding. Vessels were constructed across Moscow Oblast, Voronezh, Bryansk, and other regions between the winter of 1695 and the spring of 1696. In April 1696, an army of 75,000 men under Aleksei Shein moved toward Azov by land and river. In early May, a second fleet led by Peter I joined them. On the 27th of May, the Russian fleet sealed off Azov by sea. On the 14th of June, the Turkish fleet attempted to break through, lost two ships, and retreated. After intensive bombardment from land and sea, Russian forces broke the defensive lines on the 17th of July, and the garrison surrendered that same day.

  Victory brought construction. Between 1696 and 1711, 215 ships were built at Taganrog and Azov. Then, the Treaty of the Pruth in 1711 reversed everything: Russia returned Azov to Turkey and the Azov fleet was destroyed. Russia recaptured the city in 1737 during the Russo-Austrian-Turkish War, only to be barred by the Treaty of Nis from keeping either the fortress or a military fleet. Decades of effort came back to the same starting position.

• 6. The Crimean War Campaign

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  On the 12th of May 1855, a combined British and French force easily captured Kerch and gained access to the Sea of Azov. Ten days later, on the 22nd of May, they attacked Taganrog. Their goal was to cut off Russian supply lines to Crimea; capturing Taganrog would also expose Rostov, a key node in Russian support for Caucasian operations.

  The attack on Taganrog failed. What followed was a siege. Despite the allied forces fielding approximately 16,000 soldiers against fewer than 2,000 Russian defenders, Taganrog held. The siege ended around August 1855 with the allied army withdrawing. Individual coastal attacks along the sea continued without success and ceased in October 1855. The campaign left the Sea of Azov firmly in Russian hands and underscored how the sea's shallow waters, narrow strait, and fortified ports could neutralise superior naval forces.

• 7. 21st-Century Flashpoint

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  In December 2003, Ukraine and Russia signed a treaty agreeing to treat the Sea of Azov and the Strait of Kerch as shared internal waters. Fifteen years later, that agreement had broken down in practice. In May 2018, the Crimean Bridge opened across the Strait of Kerch. The bridge's clearance is too low to allow Panamax-sized ships to reach Ukrainian ports, effectively throttling Ukrainian maritime commerce without firing a shot.

  In September 2018, Ukraine announced plans to station navy vessels at Berdiansk. In November 2018, Russia seized three Ukrainian Navy vessels attempting to transit the Strait of Kerch and captured 24 sailors, who were held for months before being released through negotiations. On the 10th of December 2021, the Ukrainian Navy reported that Russia had blocked nearly 70 percent of the Sea of Azov, issuing navigation warnings ostensibly for artillery exercises near Mariupol, Berdyansk, and Henichesk.

  On the 24th of February 2022, Russian forces began shelling Mariupol at the outset of the full-scale invasion. By May 2022, after the siege of Mariupol ended, Russia controlled the entire northern coastline, the region known as north Pryazovia, and Ukraine had lost direct access to the sea. The major port of Mariupol, whose population the source records at 491,600, fell within the occupied zone. The Arabat Spit, a natural barrier stretching over 112 kilometres along the western shore, one of the longest spits in the world, was now on the front line of a war that ancient geographers, for all their confusion about this small sea, could never have imagined.