Command of the sea
Naval dominance ensuring free movement and denying rivals the sea.
Command of the sea, also known as sea control, describes a situation where one navy is powerful enough in a given area that its opponents cannot challenge it directly. This dominance can be limited to coastal waters or extend across entire oceans, which is what makes a navy a blue-water force. It is the naval version of air supremacy. When a country or alliance holds command of the sea, its own warships and merchant vessels can travel freely, while adversaries must either remain in port or attempt to slip past unnoticed. This control also allows for unopposed amphibious landings, opening up new ground-based strategies.
For most of the 18th through early 20th centuries, the British Royal Navy held this position, letting Britain and its allies trade and move troops and supplies easily during wars while blocking its enemies from doing the same. After World War II, the United States Navy took over that role. Few nations can maintain a blue-water navy, but many are upgrading their green-water forces to blue-water capability, which will increase military activity in foreign exclusive economic zones (the area from the coast out to 200 nautical miles) and could affect how those zones are used.
During the Age of Sail, several powers tried to extend their command into peacetime by taxing or restricting shipping on open seas. Venice, for instance, claimed the Adriatic and charged heavy fees on vessels in its northern waters. Genoa asserted control over much of the western Mediterranean. Denmark and Sweden jointly claimed the Baltic. Spain claimed the Pacific and the Gulf of Mexico, while Portugal claimed the Indian Ocean and areas east of the Tordesillas meridian in the Atlantic.
The two main asymmetric countermeasures against a dominant navy in that era were smuggling and privateering. Smuggling kept blockaded countries supplied with food and trade goods, while privateering let weaker navies disrupt the stronger power's commerce. Because these activities often involved non-governmental or criminal groups, stronger governments grew to oppose them. The 1856 Paris Declaration banned privateering; it was signed by major powers and widely accepted, though not by the US and a few others, and the ban became customary international law.
In the steam era, Germany used submarine warfare in both world wars as a modern version of privateering, targeting Allied merchant shippi
- Concept type
- Naval military concept
- Equivalent to
- Air supremacy
- Historic holder (18th–early 20th c.)
- British Royal Navy
- Post-WWII holder
- United States Navy
- Primary countermeasures (Age of Sail)
- Smuggling and privateering
- Modern countermeasure example
- Submarine warfare (Germany in WWI and WWII)
- Key treaty
- 1856 Paris Declaration Respecting Maritime Law (banned privateering; signed by major powers and widely accepted)
Lore & Background
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 claimed the Adriatic Sea, and exacted a heavy toll from vessels navigating its northern waters. Genoa claimed significant control over the western Mediterranean. Denmark and Sweden claimed to share the Baltic Sea between them. Spain claimed dominion over the Pacific Ocean and the Gulf of Mexico, and Portugal over the Indian Ocean and areas east of the Tordesillas meridian in the Atlantic. During the Age of Sail, the two primary countermeasures to another power holding contro
Reader's Guide
Command of the sea has been a decisive strategic concept in naval warfare, enabling a dominant navy to protect its own shipping and project power while denying the same to adversaries. The British Royal Navy 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 move troops and supplies easily in wartime. In the post-World War II period, the United States Navy has held command of the sea. The concept has evolved with technology: during the Age of Sail, smuggling and privateering were key countermeasures; in the era of steam, submarine warfare emerged; and in the era of naval aviation, aircraft became an effective countermeasure. Modern command of the sea requires advanced navies with surveillance satellites, submarine detection systems, and aircraft carriers. The term 'blue-water navy' is disputed, but is strongly linked to the maintenance of aircraft carriers capable of operating in the oceans. Even a blue-water navy remains vulnerable to asymmetric threats, such as land-based missiles, diesel-electric submarines, or fast attack craft, as demonstrated by the USS Cole bombing.
Did You Know?
- The British Royal Navy held command of the sea for most of the period between the 18th to the early 20th centuries.
- The 1856 Paris Declaration Respecting Maritime Law banned privateering, though it was ratified by relatively few countries.
- During World War II, aircraft became an effective countermeasure to command of the sea, since ships could not defend themselves well against air attack.
- The USS Cole was attacked by a suicide attack while in port, illustrating vulnerability of advanced navies.
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