A green-water navy is a maritime force that is capable of operating in its nation's littoral zone, and has the competency to operate in the open oceans of its surrounding region. It is a relatively new term, and has been created to better distinguish, and add nuance, between two long-standing descriptors: blue-water navy (deep ocean waters) and brown-water navy (shallow littoral waters).
As a non-doctrinal term with no concrete legal or political definition, it can be used in several different ways. It originated with the United States Navy, who use it to refer to the portion of their fleet that specializes in offensive operations in coastal waters. Nowadays such ships rely on stealth or speed to avoid destruction by shore batteries or land-based aircraft.
The US Navy has also used the term to refer to the first phase of the expansion of the Chinese Navy into a full blue-water navy. Subsequently, other authors have applied it to other national navies that can project power locally, but cannot sustain operations at range without the help of other countries. Such navies typically have amphibious ships and sometimes small aircraft carriers, which can be escorted by destroyers and frigates with some logistical support from tankers and other auxiliaries.
The elements of maritime geography are loosely defined and their meanings have changed throughout history. The US's 2010 Naval Operations Concept defines blue water as "the open ocean", green water as "coastal waters, ports and harbors", and brown water as "navigable rivers and their estuaries". Robert Rubel of the US Naval War College includes bays in his definition of brown water, and in the past US military commentators have extended brown water out to 100 nautical miles (190 km) from shore.
During the Cold War, green water denoted those areas of ocean in which naval forces might encounter land-based aircraft. The development of long-range bombers with anti-ship missiles turned most of the oceans to "green" and the term all but disappeared. After the Cold War, US amphibious task forces were sometimes referred to as the green-water navy, in contrast to the blue-water carrier battle groups. This distinction disappeared as increasing threats in coastal waters forced the amphibious ships further offshore, delivering assaults by helicopter and tiltrotor from over the horizon. This prompted the development of ships designed to operate in such waters - the Zumwalt-class destroyer and the littoral combat ships; modeling has suggested that current NATO frigates are vulnerable to swarms of 4-8 small boats in green water. Rubel has proposed redefining green water as those areas of ocean which are too dangerous for high-value units, requiring offensive power to be dispersed into smaller vessels such as submarines that can use stealth and other characteristics to survive. Under his scheme, brown water would be zones in which ocean-going units could not operate at all, including rivers, minefields, straits, and other choke points.
As the preeminent blue-water navy of the early 21st century, the US Navy is able to define maritime geography in terms of offensive action in the home waters of its enemies, without being constrained by logistics. This is not true for most other navies, whose supply chains and air cover typically limit them to power projection within a few hundred kilometers of home territory. A number of countries are working on overcoming these constraints. Other authors have started to apply the term "green-water navy" to any national navy that has ocean-going ships but lacks the logistical support needed for a blue-water navy. It is often not clear what they mean, as the term is used without consistency or precision.
A green-water navy does not mean that the individual ships of the fleet are unable to function away from the coast or in open ocean: instead, it suggests that due to logistical reasons they are unable to be deployed for lengthy periods, and must have aid from other countries to sustain long term deployments. Also the term "green-water navy" is subjective as numerous countries that do not have a true green-water navy maintain naval forces that are on par with countries that are recognized as having green-water navies. For example, the German Navy has near the same capability as the Canadian Navy but is not recognized as a true green-water navy. Another example is the Portuguese Navy that, despite being usually classified as a minor navy, has several times conducted sustained operations in faraway regions typical of the green-water navies. However, the differences between blue-water navies and brown or green-water navies are usually quite noticeable, for example, the US Navy was able to quickly respond to the disappearance of Malaysia Airlines Flight 370 and continue operations in the region with relative ease even though the search area covered the Indian Ocean. In contrast, in 2005 the then green-water Russian Navy was unable to properly respond when its AS-28 rescue vehicle became tangled in undersea cables unable to surface, relying on the blue-water Royal Navy to respond and carry out the rescue in time.
Just as nations build up naval capability, some lose it. For example, the Austro-Hungarian Navy was a modern green water navy of the time, but as the countries lost their coasts during World War I, their navies were confiscated and their ports became parts of Italy and Yugoslavia. The Axis powers lost naval capabilities after their defeat in World War II, with most of Japan's Imperial Navy and Germany's Navy being disarmed and their troop and ship numbers capped and monitored by the Allies. The collapse of the USSR also brought with it the collapse of the second-largest naval force in the world, and the largest submarine force in the world. Although the Russian Federation made sure to inherit the most capable ships, passing most older models to successor states, as it had lost the logistical capabilities of the Soviet Navy, it was no longer able to operate away from Russian shores for extended periods of time. Moreover, budget cuts forced large cuts in the submarine force, such as the retirements of the Typhoon-class submarine. As the Soviet Navy was built largely around submarine warfare the losses in the submarine capability have adversely affected the capability of the newly formed Russian Navy as well.
The Royal Australian Navy is well established as a green-water navy. The navy sustains a broad range of maritime operations, from the Middle East to the Pacific Ocean, often as part of international or allied coalitions. The RAN operates a modern fleet, consisting of destroyers, frigates, conventional submarines as well as an emerging amphibious and power projection capability based on the commissioning of HMAS Choules and two Canberra-class landing helicopter docks.
The Brazilian Navy has frequently been dubbed a "green-water" force by experts. The navy is primarily focused on securing the nation's littorals and exclusive economic zone (EEZ), but also maintains the capacity to operate in the wider South Atlantic Ocean. Since the early 2000s, the Brazilian Navy has contributed to a number of peacekeeping and humanitarian missions.
According to the criteria as outlined in the 2001 publication, "Leadmark: The Navy's Strategy for 2020", the Royal Canadian Navy had met its description of a 3rd tier "Medium Global Force Projection Navy" - a green-water navy with the capacity to project force worldwide with the aid of more powerful maritime allies (e.g. United Kingdom, France and the United States). In this context, the Royal Canadian Navy ranked itself alongside the navies of Australia and the Netherlands.
The Finnish Navy, having been given the daunting[according to whom?] task of protecting the often shallow territorial waters of Finland riddled with skerries, along with the somewhat recently added task of providing ships for international operations led by the EU, focuses on its ability to operate in shallow waters while retaining some blue-water capabilities for the larger vessels such as the decommissioned minelayer Pohjanmaa, to-be decommissioned Hämeenmaa-class minelayers and the future Pohjanmaa-class corvettes.
Pollution control vessels Louhi, Halli and Hylje, although owned by Finnish Environment Institute (SYKE), are operated by the Navy & provide logistical support and sea cable laying for the Navy as well as act as mother ships for diving operations.
The Japan Maritime Self-Defense Force is considered to be a green-water navy. Overseas JMSDF deployments include participation in the Combined Task Force 150, and an additional task force in the Indian Ocean from 2009 to combat piracy in Somalia. The first postwar overseas naval air facility of Japan was established next to Djibouti-Ambouli International Airport.
The Royal Netherlands Navy has been officially described as a 3rd tier "Medium Global Force Projection Navy" - or a green-water navy with the capacity to project force worldwide with the aid of more powerful maritime allies (e.g. Britain, France and the United States). In this context, the Royal Netherlands Navy ranks alongside the navies of Australia and Canada, while the USN is a 1st tier global blue-water navy and Britain and France are 2nd tier blue-water navies. For many years since the end of the Cold War, the Royal Netherlands Navy has been changing its role from national defence to overseas intervention.
The Spanish Navy is a green-water navy, and participates in joint operations with NATO and European allies around the world. The fleet has 54 commissioned ships, including; one amphibious assault ship (also used as an aircraft carrier), two amphibious transport docks, 5 AEGIS destroyers (5 more under construction), 6 frigates, 7 corvettes (2 more under construction) and three conventional submarines. (4 under construction)
The Republic of Korea Navy is considered to be a green-water navy. In 2011, the government authorized the building of a naval base on Jeju Island to support the new Dokdo-class amphibious assault ships, the base will also be capable of supporting joint forces with the US Navy. A ski-jump for the operation of V/STOL jet fighters is being considered for the second ship of the Dokdo class. The Korean government is considering to buy surplus Harriers as a possible interim for the F-35 Lightning II if they choose to operate VTOL aircraft at all.