The term blue-water navy is a colloquialism used to describe a maritime force capable of operating across the deep waters of open oceans. While what actually constitutes such a force remains undefined, there is a requirement for the ability to exercise sea control at wide ranges. The term used in the United Kingdom is expeditionary.

Capabilities of a blue-water navy

"Blue-water" (high seas) naval capability means that a fleet is able to operate on the "high seas." While traditionally a distinction was made between the coastal brown-water navy (operating in the littoral zone to 200 nautical miles (370 km)) and a seagoing blue-water navy, a new term "green-water navy" has been created by the U.S. Navy. Green-water navy appears to be equivalent to a brown-water navy in older sources. The term brown-water navy appears to have been reduced in U.S. Navy parlance to a riverine force.

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 ice shelf.

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 Zones [littoral zone to 200 nautical miles (370 km)] with possible repercussions for the EEZ regime."

As there is no clear definition of a blue-water navy, the status is disputed. Usually it is 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's last aircraft carrier, HMAS Melbourne. Senior navy 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 Australia "would no longer have a blue-water navy (one capable of operating away from friendly coasts)."

The term blue-water navy should not be mixed up with brown, green and blue water capability or ship. U.S. Navy Chief of Naval Operations Admiral Michael Mullen pointed out in an interview with KQV (Pittsburgh): "We are looking at, in addition to the blue-water ships which I would characterize and describe as our aircraft carriers and other ships that support that kind of capability, we're also looking to develop capability in what I call the green-water and the brown-water, and the brown-water is really the rivers . . . These are challenges we all have, and we need to work together to ensure that the sea lanes are secure." The capability for blue, green or brown water depends on the vessel's specifications. The vessels of a green-water navy can often operate in blue-water for example. A number of nations have extensive maritime assets but lack the capability to maintain the required sustainable logistic reach. Some of them join coalition task groups in blue-water deployments.

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 assets, 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.

Examples of operating blue-water navies

These are navies that have successfully used the capabilities of their blue-water navies to exercise control at high seas and from there have projected power into other nations' littoral waters.

• The United States Navy maintains eleven Carrier Strike Groups (one centered on USS Enterprise, the remainder on Nimitz class carriers), of which six are deployed or ready for deployment within 30 days, and two ready for deployment within 90 days under the Fleet Response Plan (FRP). The US Navy also maintains a posture of Continuous At Sea Deterrence (CASD) through the Trident submarine-launched ballistic missiles on Ohio-class submarines. It also maintains a continuous deployment of Expeditionary Strike Groups that embark a Marine Expeditionary Unit with an Aviation Combat Element of Landing Helicopter Docks and Landing Helicopter Assault.

• The United Kingdom's Royal Navy maintains two task forces concurrently (one based around an aircraft carrier and one based around an Amphibious assault ship). At least one task group is deployed at any one time. There are currently two Invincible-class aircraft carriers in operation, with a further one in reserve. The Royal Navy also uses the Ocean-class Landing Platform, Helicopter (LPH) as well as the two Albion-class amphibious transport docks as the centre of a task group. The Royal Navy maintains a Continuous At Sea Deterrence policy via its Vanguard-class ballistic missile submarines utilising Trident missiles. The Royal Navy also supports a number of standing commitments worldwide on a continuous basis.

• The Russian Navy maintains a Carrier Battle Group around Admiral Kuznetsov and multiple Surface Action Groups centered around nuclear-powered Large Battle Cruisers of Kirov Class. Russia also maintains a posture of Continuous At Sea Deterrence (CASD) with its ballistic missile submarine fleet, comparable to United States Navy.

• The French Navy (Marine Nationale) has the ability to deploy an aircraft-carrier-based task group and maintains a Continuous At Sea Deterrence included in the Force Océanique Stratégique (Strategic Oceanic Force). France also has a wide range of naval deployments throughout the world.

Navies with limited blue water capabilities

The Indian Navy maintains a Carrier Battle Group around INS Viraat and can project power throughout the Indian Ocean. India launched an SSBN INS Arihant in July 2008, to act as a nuclear deterrent at sea. India has two aircraft carriers under construction that are due to join the fleet in 2014.

Several other countries maintain navies capable of some "blue water operation". Italy, and Spain all operate aircraft carriers. Brazil owns a carrier currently undergoing upgrades and Thailand owns a Spanish-built carrier that is largely inactive. Many navies, including Japan, China, Canada and Australia, operate a limited number of ships far from their home waters either alone or in coordination with true "blue water navies". None of these operate aircraft carriers.

See also

• Brown-water navy

• Green-water navy