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Command of the sea (also called control of the sea or sea control) is a naval military concept regarding the strength of a particular
navy A navy, naval force, military maritime fleet, war navy, or maritime force is the military branch, branch of a nation's armed forces principally designated for naval warfare, naval and amphibious warfare; namely, lake-borne, riverine, littoral z ...
to a specific naval area it controls. A navy has command of the sea when it is so strong that its rivals cannot attack it directly. This dominance may apply to its surrounding waters (i.e., the
littoral The littoral zone, also called litoral or nearshore, is the part of a sea, lake, or river that is close to the shore. In coastal ecology, the littoral zone includes the intertidal zone extending from the high water mark (which is rarely i ...
) or may extend far into the oceans, meaning the country has a
blue-water navy A blue-water navy is a Navy, maritime force capable of operating globally, essentially across the deep waters of open oceans. While definitions of what actually constitutes such a force vary, there is a requirement for the ability to exercise Co ...
. It is the naval equivalent of air supremacy. With command of the sea, a country (or alliance) can ensure that its own military and merchant ships can move around at will, while its rivals are forced either to stay in port or to try to evade it. It also enables free use of
amphibious operations Amphibious warfare is a type of Offensive (military), offensive military operation that today uses naval ships to project ground and air power onto a hostile or potentially hostile shore at a designated landing beach. Through history the opera ...
that can expand ground-based strategic options. The British
Royal Navy The Royal Navy (RN) is the naval warfare force of the United Kingdom. It is a component of His Majesty's Naval Service, and its officers hold their commissions from the King of the United Kingdom, King. Although warships were used by Kingdom ...
held command of the sea for most of the period between the 18th to the early 20th centuries, allowing Britain and its allies to trade and to move troops and supplies easily in wartime, while its enemies could not. In the post-
World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
period, the
United States Navy The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...
has had command of the sea. Few navies can operate as blue-water navies, but "many States are converting green-water navies to blue-water navies and this will increase military use of foreign
Exclusive Economic Zone An exclusive economic zone (EEZ), as prescribed by the 1982 United Nations Convention on the Law of the Sea, is an area of the sea in which a sovereign state has exclusive rights regarding the exploration and use of marine natural resource, reso ...
s ittoral zone to 200 nautical miles (370 km)with possible repercussions for the EEZ regime."


Historic command of the sea during the age of sail


National capabilities

Historically, many powers attempted to extend command of the sea into peacetime, imposing taxes or other restrictions on shipping using areas of open sea. For example,
Venice Venice ( ; ; , formerly ) is a city in northeastern Italy and the capital of the Veneto Regions of Italy, region. It is built on a group of 118 islands that are separated by expanses of open water and by canals; portions of the city are li ...
claimed the
Adriatic Sea The Adriatic Sea () is a body of water separating the Italian Peninsula from the Balkans, Balkan Peninsula. The Adriatic is the northernmost arm of the Mediterranean Sea, extending from the Strait of Otranto (where it connects to the Ionian Se ...
, and exacted a heavy toll from vessels navigating its northern waters.
Genoa Genoa ( ; ; ) is a city in and the capital of the Italian region of Liguria, and the sixth-largest city in Italy. As of 2025, 563,947 people live within the city's administrative limits. While its metropolitan city has 818,651 inhabitan ...
and
France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...
each claimed portions of the western
Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...
.
Denmark Denmark is a Nordic countries, Nordic country in Northern Europe. It is the metropole and most populous constituent of the Kingdom of Denmark,, . also known as the Danish Realm, a constitutionally unitary state that includes the Autonomous a ...
and
Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...
claimed to share the
Baltic Sea The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by the countries of Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden, and the North European Plain, North and Central European Plain regions. It is the ...
between them.
Spain Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...
claimed dominion over the
Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...
and the
Gulf of Mexico The Gulf of Mexico () is an oceanic basin and a marginal sea of the Atlantic Ocean, mostly surrounded by the North American continent. It is bounded on the northeast, north, and northwest by the Gulf Coast of the United States; on the southw ...
, and
Portugal Portugal, officially the Portuguese Republic, is a country on the Iberian Peninsula in Southwestern Europe. Featuring Cabo da Roca, the westernmost point in continental Europe, Portugal borders Spain to its north and east, with which it share ...
over the
Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or approximately 20% of the water area of Earth#Surface, Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia (continent), ...
and all the
Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...
south of
Morocco Morocco, officially the Kingdom of Morocco, is a country in the Maghreb region of North Africa. It has coastlines on the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to Algeria–Morocc ...
(Hall, 148-9).


Asymmetric countermeasures

During the
age of sail The Age of Sail is a period in European history that lasted at the latest from the mid-16th (or mid-15th) to the mid-19th centuries, in which the dominance of sailing ships in global trade and warfare culminated, particularly marked by the int ...
, there were two primary counter measures to another power holding control of the sea:
smuggling Smuggling is the illegal transportation of objects, substances, information or people, such as out of a house or buildings, into a prison, or across an international border, in violation of applicable laws or other regulations. More broadly, soc ...
, and
privateering A privateer is a private person or vessel which engages in commerce raiding under a commission of war. Since Piracy, robbery under arms was a common aspect of seaborne trade, until the early 19th century all merchant ships carried arms. A sover ...
. Smuggling helped to ensure that a country could continue trading (and obtaining food and other vital supplies) even when under blockade, while privateering allowed the weaker power to disrupt the stronger power's trade. As these measures, which are examples of
asymmetric warfare Asymmetric warfare (or asymmetric engagement) is a type of war between belligerents whose relative military power, strategy or tactics differ significantly. This type of warfare often, but not necessarily, involves insurgents, terrorist grou ...
, came from non-governmental and sometimes criminal organizations, they fell into disfavor with stronger governments. The 1856 Paris Declaration Respecting Maritime Law banned privateering. That treaty was ratified by relatively few countries, but has become the customary law of the sea.


Historic command of the sea in the era of steam

A more modern countermeasure, similar to privateering, was the use of
submarine warfare Submarine warfare is one of the four divisions of underwater warfare, the others being anti-submarine warfare, Naval mine, mine warfare and Naval mine, mine countermeasures. Submarine warfare consists primarily of Diesel engine, diesel and nu ...
by Germany during
World War I World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...
and
World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
to attack allied merchant shipping primarily in the
Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...
,
Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...
, and
Baltic Sea The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by the countries of Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden, and the North European Plain, North and Central European Plain regions. It is the ...
.


Historic command of the sea in the era of naval aviation

During
World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
,
aircraft An aircraft ( aircraft) is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using either Buoyancy, static lift or the Lift (force), dynamic lift of an airfoil, or, i ...
also became an effective countermeasure to command of the sea, since ships could not defend themselves well against air attack. The
Battle of Britain The Battle of Britain () was a military campaign of the Second World War, in which the Royal Air Force (RAF) and the Fleet Air Arm (FAA) of the Royal Navy defended the United Kingdom (UK) against large-scale attacks by Nazi Germany's air force ...
was largely an attempt by Germany to eliminate the
Royal Air Force The Royal Air Force (RAF) is the Air force, air and space force of the United Kingdom, British Overseas Territories and Crown Dependencies. It was formed towards the end of the World War I, First World War on 1 April 1918, on the merger of t ...
, so that it would not be able to defend the
Royal Navy The Royal Navy (RN) is the naval warfare force of the United Kingdom. It is a component of His Majesty's Naval Service, and its officers hold their commissions from the King of the United Kingdom, King. Although warships were used by Kingdom ...
from air attack and even to allow a maritime invasion of Great Britain proper. The entire Japanese naval strategy during World War II in the Pacific was to acquire command of the sea by largescale destruction of Allied naval power, until their fleet was either destroyed or rendered irrelevant by the
Battle of Leyte Gulf The Battle of Leyte Gulf () 23–26 October 1944, was the largest naval battle of World War II and by some criteria the largest naval battle in history, with over 200,000 naval personnel involved. By late 1944, Japan possessed fewer capital sh ...
giving command of the sea to the Allies.


Modern command of the sea

Advanced navies, with access to surveillance satellites and large-scale submarine detection systems, can rarely be surprised at sea, but cannot be everywhere. Individual ships of advanced navies can be vulnerable at sea (e.g., the hit by an Iraqi aircraft-delivered anti-ship missile while patrolling the
Persian Gulf The Persian Gulf, sometimes called the Arabian Gulf, is a Mediterranean seas, mediterranean sea in West Asia. The body of water is an extension of the Arabian Sea and the larger Indian Ocean located between Iran and the Arabian Peninsula.Un ...
) or in port (e.g., by the
suicide attack A suicide attack (also known by a wide variety of other names, see below) is a deliberate attack in which the perpetrators knowingly sacrifice their own lives as part of the attack. These attacks are a form of murder–suicide that is ofte ...
on the .) " Blue-water" naval capability means that a fleet is able to operate on the "
high seas The terms international waters or transboundary waters apply where any of the following types of bodies of water (or their drainage basins) transcend international boundaries: oceans, large marine ecosystems, enclosed or semi-enclosed regiona ...
." While traditionally a distinction was made between the coastal
brown-water navy A brown-water navy or riverine navy, in the broadest sense, is a naval force capable of military operations in inland waters (rivers, lakes and inland seas) and nearshores. The term originated in the United States Navy during the American Ci ...
, operating in the
littoral zone The littoral zone, also called litoral or nearshore, is the part of a sea, lake, or river that is close to the shore. In coastal ecology, the littoral zone includes the intertidal zone extending from the high water mark (which is rarely flood ...
to 200 nautical miles (370 km), and a seagoing blue-water navy, a new term, "
green-water navy A green-water navy is a maritime force that is capable of operating in its state's littoral zones and has limited competency to operate in the surrounding marginal seas. It is a relatively new term, and has been created to better distinguish ...
," has been created by the U.S. Navy, which refers to the coastal submarines and fast attack boats of many nations, the larger littoral combat corvettes and similar vessels of a substantial number of powers, and amphibious vessels ranging from elderly LSTs to complex S/VTOL carriers and other specialized ships. In modern warfare blue-water navy implies self-contained force protection from sub-surface, surface and airborne threats and a sustainable logistic reach, allowing a persistent presence at range. In some maritime environments such a defence is given by natural obstacles, such as the
Arctic The Arctic (; . ) is the polar regions of Earth, polar region of Earth that surrounds the North Pole, lying within the Arctic Circle. The Arctic region, from the IERS Reference Meridian travelling east, consists of parts of northern Norway ( ...
ice shelf. The
US Navy The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...
studied a concept for an economically priced ship capable of surface and subsurface sea control with ASW helicopters and STOVL fighters for light air defense but not large enough to be well suited to power projection known as a Sea Control Ship. This small aircraft carrier was not built by the US although a long deck
Amphibious assault ship An amphibious assault ship is a type of warship employed to land and support ground forces on enemy territory during an armed conflict. The design evolved from aircraft carriers converted for use as helicopter carriers (which, as a result, ar ...
equipped with STOVL fighters and ASW helicopters instead of its primary transport helicopters is operating in a secondary sea control role.


Requirements for modern sea control

During the
Falklands War The Falklands War () was a ten-week undeclared war between Argentina and the United Kingdom in 1982 over two British Overseas Territories, British dependent territories in the South Atlantic: the Falkland Islands and Falkland Islands Dependenci ...
, the British lacked long-range Airborne Warning and Control System (AWACS), which led to ship losses and major damage to others, when the Argentinian attack aircraft came into the view of ship radar at approximately the same time they would fire antiship missiles, and only a short time before they made bombing attacks. A number of navies have learned this lesson. Many navies with
STOVL A short take-off and vertical landing aircraft (STOVL aircraft) is a fixed-wing aircraft that is able to take off from a short runway (or take off vertically if it does not have a heavy payload) and land vertically (i.e. with no runway). The ...
carriers have developed helicopter-mounted AWACS like the British and Spanish Westland Sea King AEW, Italian EH-101 AEW, and the Russian Ka-31 AEW helicopter. Recently the French with a new larger CATOBAR
aircraft carrier An aircraft carrier is a warship that serves as a seagoing airbase, equipped with a full-length flight deck and hangar facilities for supporting, arming, deploying and recovering carrier-based aircraft, shipborne aircraft. Typically it is the ...
obtained the US
E-2 Hawkeye The Northrop Grumman E-2 Hawkeye is an American all-weather, carrier-capable tactical airborne early warning (AEW) aircraft. This twin-turboprop aircraft was designed and developed during the late 1950s and early 1960s by the Grumman Aircraft ...
AWACS aircraft. An example for the difference between a blue-water navy and a green-water navy: "...The first should be a 'green-water active defense' that would enable the
People's Liberation Army Navy The People's Liberation Army Navy, also known as the People's Navy, PLA Navy or simply Chinese Navy, is the naval warfare military branch, branch of the People's Liberation Army, the national military of the People's Republic of China. It i ...
to protect China's territorial waters and enforce its sovereignty claims in the
Taiwan Strait The Taiwan Strait is a strait separating the island of Taiwan and the Asian continent. The strait is part of the South China Sea and connects to the East China Sea to the north. The narrowest part is wide. Names Former names of the Tai ...
and the
South China Sea The South China Sea is a marginal sea of the Western Pacific Ocean. It is bounded in the north by South China, in the west by the Indochinese Peninsula, in the east by the islands of Taiwan island, Taiwan and northwestern Philippines (mainly Luz ...
. The second phase would be to develop a blue-water navy capable of projecting power into the western Pacific . . . Liu Central Military Commission 1989-97">Central Military Commission (China)">Central Military Commission 1989-97believed that in order to fulfill a blue-water capability, the PLAN had to obtain aircraft carriers . . ."
Aircraft carrier An aircraft carrier is a warship that serves as a seagoing airbase, equipped with a full-length flight deck and hangar facilities for supporting, arming, deploying and recovering carrier-based aircraft, shipborne aircraft. Typically it is the ...
s are deployed with other specialized vessels in carrier battle groups, providing protection against sub-surface, surface and airborne threats. As there is no clear definition of a blue-water navy, the status is disputed. Given the importance of naval aviation, the term may be considered to be strongly linked to the maintenance of aircraft carriers capable of operating in the oceans. "In the early 80s there was a bitter and very public battle fought over whether or not to replace
Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
's last aircraft carrier, HMAS ''Melbourne''. Senior
Royal Australian Navy The Royal Australian Navy (RAN) is the navy, naval branch of the Australian Defence Force (ADF). The professional head of the RAN is Chief of Navy (Australia), Chief of Navy (CN) Vice admiral (Australia), Vice Admiral Mark Hammond (admiral), Ma ...
personnel warned without a carrier, Australia would be vulnerable to all types of threat. One ex-Chief of Navy went so far as to claim that we" (the Australians) "would no longer have a blue-water navy (one capable of operating away from friendly coasts)." Yet although the
Royal Thai Navy The Royal Thai Navy (Abbreviation, Abrv: RTN, ทร.; , ) is the Navy, naval warfare force of Thailand. Established in 1906, it was modernised by the Admiral Prince Abhakara Kiartiwongse (1880–1923) who is known as the father of the Royal N ...
operates a sea-going carrier, the RTN is not absolutely a "blue-water navy."


Countermeasures to imposed command

While a ''blue-water navy'' can project sea control power into another nation's littoral, it remains susceptible to threats from less capable forces. Sustainment and logistics at range yield high costs and there may be a saturation advantage over a deployed force through the use of land-based air or
surface-to-surface missile A surface-to-surface missile (SSM) is a missile designed to be launched from the ground or the sea and strike targets on land or at sea. They may be fired from hand-held or vehicle mounted devices, from fixed installations, or from a ship. They ar ...
assets (whether on terrain-following or ballistic trajectories), diesel-electric submarines, or asymmetric tactics such as Fast Inshore Attack Craft. An example of this vulnerability was the October 2000 USS ''Cole'' bombing in
Aden Aden () is a port city located in Yemen in the southern part of the Arabian peninsula, on the north coast of the Gulf of Aden, positioned near the eastern approach to the Red Sea. It is situated approximately 170 km (110 mi) east of ...
. In response to these threats, the U.S. Navy has developed the Littoral Combat Ship (LCS).


See also

* '' Battleplan'' (documentary TV series) * Air supremacy * Naval blockade *
Sea denial Sea denial is a military term for preventing an enemy from using the sea. It is a naval warfare subset of anti-access/area denial (A2/AD) strategies, and does not necessarily mean that the denier itself will use the sea. It is a parallel concept ...
*
Alfred Thayer Mahan Alfred Thayer Mahan (; September 27, 1840 – December 1, 1914) was a United States Navy officer and historian whom John Keegan called "the most important American strategist of the nineteenth century." His 1890 book '' The Influence of Sea Pow ...
*
Maritime republics The maritime republics (), also called merchant republics (), were Italian Thalassocracy , thalassocratic Port city, port cities which, starting from the Middle Ages, enjoyed political autonomy and economic prosperity brought about by their mar ...
* Maritime power *
Thalassocracy A thalassocracy or thalattocracy, sometimes also maritime empire, is a state with primarily maritime realms, an empire at sea, or a seaborne empire. Traditional thalassocracies seldom dominate interiors, even in their home territories. Examples o ...


References


Notes


Sources

* WE Hall, ''Treatise on International Law'', 4th ed., 1895.


Further reading

* Baer, George W. ''One Hundred Years of Sea Power: The U.S. Navy, 1890–1990'' (Stanford University Press, 1993). * Beiriger, Eugene Edward. “Building a Navy ‘Second to None’: The U.S. Naval Act of 1916, American Attitudes toward Great Britain, and the First World War," ''British Journal for Military History'' 3, no. 3 (2017): 4–29. https://bjmh.gold.ac.uk/article/view/755/877. * Bruns, Sebastian. ''US Naval Strategy and National Security: The Evolution of American Maritime Power'' (Routledge, 2018). * Caverley, Jonathan D., and Peter Dombrowski. "Too important to be left to the admirals: the need to study maritime great-power competition." ''Security Studies'' 29#4 2020 pp.579–600 https://doi.org/10.1080/09636412.2020.1811448 * Gray, Colin S. ''The Leverage of Sea Power: The Strategic Advantage of Navies in War'' (Free Press, 1992) * Grove, Eric. ''The future of sea power'' (Taylor & Francis, 2021
online
* Grygiel, Jakub J. "The Limits of Sea Power." ''Naval War College Review'' 74.4 (2021): 95–110
online
* Heginbotham, Eric. and Richard J. Samuels. “Active Denial: Redesigning Japan’s Response to China’s Military Challenge,” ''International Security'' 42#4 (2018): 128–69. * Hou, Kuang-hao. "The Social Construction of the Ocean, Sea Power, and Maritime Transformation." ''Journal of Political & Military Sociology'' 50.1 (2023). * Kennedy, Paul. “The Influence and the Limitations of Sea Power,” ''International History Review'' 10#1 (1988): 2–17. * Kirchberger, Sarah. ''Assessing China’s Naval Power: Technological Innovation, Economic Constraints, and Strategic Implications'' (Springer-Verlag GmbH, 2018). * Lambert, Nicholas A. ''The Neptune Factor: Alfred Thayer Mahan and the Concept of Sea Power'' (Naval Institute Press, 2024). * Lambert, Nicholas A. ''Planning Armageddon: British Economic Warfare and the First World War'' (Harvard University Press, 2012). * Lambert, Andrew. ''Seapower States: Maritime Culture, Continental Empires and the Conflict that Made the Modern World'' (Yale UP, 2018) * Mahan, Alfred Thayer. ''Mahan on Naval Strategy: Selections from the Writings of Rear Admiral Alfred Thayer Mahan'' (Naval Institute Press, 1991). * Mahan, Alfred Thayer. ''The Influence of Sea Power upon History'' (1890) * Morton, John Fass. ''Sea Power and the American Interest: From the Civil War to the Great War'' (Naval Institute Press, 2024
online review of this book
* Semmel, Bernard. ''Liberalism and naval strategy: ideology, interest and sea power during the Pax Britannica'' (Routledge, 2023). * Till, Geoffrey. ''Seapower: A Guide for the Twenty-First Century'' (2nd ed. Routledge, 2009) * Young, Thomas-Durell. “NATO’s Selective Sea Blindedness: Assessing the Alliance’s New Navies,” ''Naval War College Review'' 72#3 (2019): 13–39. * Zafar, Javed. "The Elements of Sea Power and the Indo-Pacific Strategy of the West Asian Region." ''MJIR, Malaysian Journal of International Relations'' 11.1 (2023): 20–42
online
{{Authority control Naval warfare Military doctrines