History

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Early origins and wartime legacy

The presence of munitions in European seas is the result of more than a century of military activity, technological development and disposal practices. Although weapons and military materials had entered marine waters earlier, the modern legacy developed during the 19th century with advances in explosive ordnance, artillery and naval warfare. The scale of contamination increased dramatically during the two World Wars and through the subsequent disposal of surplus and captured military stocks.

The development of breech-loading artillery, explosive-filled shells, naval mines and increasingly powerful naval weapons resulted in growing quantities of military material entering marine waters. These weapons were deployed from coastal fortifications, naval vessels and, later, aircraft. Military engagements, training exercises and weapons testing led to munitions being fired, dropped or lost at sea. Although these early inputs were relatively limited compared with those of the 20th century, they marked the beginning of a long-term accumulation of military materials on the seabed.

During the First and Second World Wars, Europe’s seas became major theatres of military operations. Naval warfare, aerial bombardment and coastal artillery resulted in substantial quantities of unexploded ordnance remaining on the seabed. Sea mines were deployed extensively to restrict shipping routes, protect ports and defend strategically important areas, particularly in the North Sea, the Baltic Sea and the English Channel. Torpedoes, aerial bombs, depth charges and artillery shells were also used in large numbers, with many failing to detonate and remaining where they came to rest.

Further sources include shipwrecks and sunken vessels that still contain ammunition, explosive cargo or fuel, as well as munitions lost during military exercises, transport and testing activities. These wartime inputs created a highly dispersed and uneven distribution of munitions across European waters. In some areas, individual items are scattered over large parts of the seabed, while in others they are concentrated around former battlefields, minefields, bombing ranges, ports and shipwrecks.

Post-war dumping and disposal practices

Disposal at sea was already used following the First World War, but the practice expanded dramatically after 1945, when European countries and the Allied powers had to manage vast quantities of surplus, obsolete and captured munitions. At the time, disposal at sea was widely regarded as a practical, efficient and low-cost solution.

Between 1945 and the early 1970s, millions of tonnes of conventional and chemical munitions were deliberately dumped in European seas. Disposal operations often took place at designated sites located near ports, in deeper offshore waters or in areas considered unsuitable for fishing and navigation. In practice, however, munitions were also frequently jettisoned before vessels reached the designated dumping grounds, particularly when transport conditions were difficult or disposal operations had to be completed quickly. As a result, the distribution of dumped munitions is considerably broader and less predictable than official dumping-site records suggest.

The available quantities and locations should therefore be understood as estimates rather than as a complete inventory. Records were frequently incomplete, lost or destroyed, disposal did not always take place within designated areas, and navigation technologies were considerably less precise than those available today. Munitions may also have been redistributed over time by currents, sediment movement, trawling, dredging and other human activities.

A particularly significant component of post-war dumping involved chemical munitions containing chemical warfare agents such as mustard gas, lewisite and tabun. These were disposed of in large quantities, either as individual shells, bombs and containers or by scuttling entire vessels loaded with munitions. Chemical weapons were often taken to deeper offshore basins, including the Bornholm and Gotland Basins in the Baltic Sea, while ships carrying chemical munitions were scuttled in areas such as the Skagerrak. Conventional munitions were also dumped extensively, including in relatively shallow waters and in areas close to coasts, ports and major transport routes.

→ All European sea basins are affected by these historical inputs.

The Baltic Sea is among the most heavily contaminated regions, with large quantities of both chemical and conventional munitions resulting from wartime activities and post-war dumping. The semi-enclosed nature of the sea, combined with slow water exchange, increases the persistence of contaminants. In the North Sea and North-East Atlantic, extensive dumping took place in areas such as Beaufort’s Dyke, where over one million tonnes of munitions were disposed of, as well as in the Skagerrak and various coastal zones. In the Mediterranean, munitions entered the marine environment primarily through wartime losses, with more limited but documented dumping activities, including in the Adriatic Sea. A notable example is the 1943 air raid on Bari, where chemical agents were released into the marine environment following the destruction of a cargo vessel. In the Black Sea, disposal activities and military use have left munitions in deeper offshore areas, particularly along the western and southern coasts.

Continuing inputs and growing recognition

During the main period of dumping, particularly between 1945 and the early 1970s, activities were carried out with limited environmental oversight and often incomplete documentation. Large-scale deliberate dumping largely ceased during the 1970s as national practices changed and regional and global controls entered into force, including the Oslo Convention in 1974 and the London Convention in 1975.

Munitions nevertheless continued to enter European waters through military training and testing, accidental losses, shipwrecks and armed conflicts. Conflicts in South-Eastern Europe during the 1990s, including those associated with the break-up of Yugoslavia, introduced additional munitions into parts of the Adriatic Sea. More recently, military activity in the Black Sea region has added new sea mines, missiles, bombs and other explosive ordnance to an already complex historical legacy.

For much of the second half of the 20th century, munitions in the sea were primarily regarded as a military, navigational and occupational safety issue. Information remained dispersed across military archives, hydrographic records, fisheries reports and national authorities, while the full quantities and locations of munitions were rarely known.

From the late 20th century onwards, scientific research, national surveys and regional cooperation gradually broadened understanding of the issue. New technologies made it possible to locate and investigate previously undocumented objects, while environmental and civil-society organisations in different parts of Europe drew greater attention to the environmental and public-interest dimensions of submerged conventional and chemical munitions. From the mid-2000s, organisations such as NABU and other marine conservation groups gave the issue greater visibility, particularly in the North and Baltic Seas. At the global level, discussions within the Organisation for the Prohibition of Chemical Weapons, supported over many years by the International Dialogue on Underwater Munitions, helped bring sea-dumped chemical weapons to wider international attention.

At the same time, the expansion of offshore wind energy, subsea cables, pipelines, dredging and other forms of seabed development increased the number of encounters with historical munitions. Expertise that had previously been concentrated largely within navies and military explosive ordnance disposal units increasingly developed into a specialised civilian and commercial field. Marine survey companies, UXO consultancies and commercial explosive ordnance disposal operators became an established part of the offshore sector, supported by the development of marine-specific professional guidance and standards. In 2014, an International Mine Action Standard specifically addressing underwater survey and clearance was introduced.

Regional institutions also began to address the legacy more systematically. In the Baltic Sea, earlier work on dumped chemical munitions developed into broader cooperation on hazardous submerged objects through HELCOM and its Expert Group on Environmental Risks of Hazardous Submerged Objects, known as EG SUBMERGED.

At the European level, the issue gradually moved from individual national initiatives and research projects towards greater regional cooperation and political recognition. Initiatives such as the JPI Oceans Joint Action on Munitions in the Sea, launched in 2015, helped coordinate expertise, identify priorities and raise the topic at the European level. Between 2020 and 2023, the NATO Science and Technology Organization’s Research Task Group AVT-RTG-330 also examined the impact of underwater dumped munitions on maritime safety, security and sustainable remediation, bringing together national approaches and highlighting the issue’s relevance for NATO. The European Union supported studies, research projects and coordination activities and increasingly incorporated underwater unexploded ordnance into its work on the marine environment, offshore development and maritime security. More recently, the European Ocean Pact announced the development of a comprehensive European strategy addressing unexploded ordnance in European seas.

Today, munitions are known to occur across large areas of the seabed in coastal and offshore environments, including as individual unexploded items, former minefields, concentrated dumping sites, ammunition cargoes and munition-bearing wrecks. Their distribution reflects successive layers of technological development, armed conflict, military activity and disposal practice.

While this historical overview focuses primarily on European waters, comparable legacies of wartime use, military losses and disposal at sea are found in many other parts of the world. Munitions in the sea are therefore both a regional historical legacy and a global consequence of past and continuing military activity.

Acknowledgement: This article is under development and is primarily based on the following key sources.