Thursday, June 17, 2010

What is Green Water?


Advocates of building out a balanced force structure consisting of larger numbers of smaller, shallow draft ships to complement a smaller number of higher end surface combatants often use the term "green water" to characterize the environment where a smaller vessel capability would operate. But what does green water really mean? During a recent CSBA workshop on maritime irregular warfare, a lively debate ensued on this issue, without much consensus.

The NOC delineates three categories which one might assume are included to help differentiate operating environments and steer the range of capabilities that might be required by naval forces in those areas:

"Blue water refers to the open ocean; green water refers to coastal waters, ports and harbors; and brown water refers to navigable rivers and their estuaries." The distinction is important, not just from an operating paradigm, but in relation to the spectrum of future (and current) naval force structures.

An advocate of exclusively high end ships would be quick to point out that large combatants are equally capable of operating in coastal waters. Which of course is true, as deep draft cruisers, destroyers, and amphibious ships frequently perform missions in areas near the OPLATs in the Northern Arabian Gulf or within sight of land off various third world coasts. Because blue water ships are capable of operating in coastal areas, one will frequently hear the argument that a force of less green water ships to complement multi-mission blue water ships isn't required.

Balanced force "green water" evangelists must challenge this logic. In an effort further the discourse, let me suggest a new definition for consideration: green water is a maritime environment in which a large naval vessel is unable to perform effectively due to any number of operational constraints. These reasons could include, but are not limited to:

Draft - The most obvious limitation of large ships in coastal areas is hydrography. For example, the LCS' 15 foot draft opens up the number of ports that the Navy can access globally from 362 to 1,111. Extrapolated from the number ports to actual of square miles of acessible waterspace, a 15-20 feet less draft makes a considerable impact and a sub-10 foot draft exponentially more so. As much as we may want to relive the glory days of WWII and Cold War naval operations, the more likely scenario is that current and future operations and conflicts will occur in the littorals. The ability to operate in nearly every square meter of water is an imperative to exercising US sea power globally.

Partner Force Overmatch - When working with nascent navies, employing billion dollar vessels that in some cases represents a significant percentage of a partner nation's GDP makes little sense. At best, utilizing larger surface combatants even in exercise roles can be patronizing or intimidating. Small navies more readily identify with vessels that are actually within the realm of the possible for them to procure, operate, and maintain.
Sovereignity Considerations - In a scenario where the US Navy operationally supports a partner nation in a FID role in coastal waters, the host nation would probably like to minimize the perception of US involvement. Large, overtly-US ships conducting MSO or other missions inside territorial waters may create a sense of illegitimacy toward the host-nation government. Ironically, the same constraint applies even to HA/DR operations in situations where host government control is tenuous. Deploying our large blue-water hospital ships in such an environment isn't advisable if a lower profile vessel with adequate medical capability is available.
Enemy Decision Cycle - In an hybrid warfare environment, a stateless enemy with only a handful of higher end, state-provided, sea denial capabilities such as anti-ship cruise missiles will likely choose his targets carefully to maximize impact at a minimal cost. A capital surface combatant off the coast makes a more tempting and high profile target than a larger number of smaller green water combatants.

Vulnerability to Sea Denial Threats - Although losing the initiative in naval warfare is always tactically unwise; recent history, culture, and ROE leads one to the conclusion that US surface ships usually take the first hit upon initiation of hostilities at sea. Given this probability, smaller, less expensive vessels should be stationed closer to shore than large ships where land-based enemy sea denial threats such as ASCMs, FAC swarm attacks, mines, or any combination of those may be expected. Although unpleasant to think about, the loss of a billion+ dollar combatant and hundreds of Sailors is much less palatable to the American people than a couple dozen Sailors and a sub-one hundred million dollar vessel. The oft-heard counter-argument is that larger ships are more survivable than smaller ships; in future posts, we'll explore that contention in more detail.

The above green water definition is admittedly imperfect; however the debate of high end only versus balanced force must take into account non-traditional constraints to blue water ship operations in the littorals. A corollary of this definition that favors maintenance of a robust force of large combatants is that smaller vessels are often unable to operate independently for any duration in "blue water" due to considerations such as range or sea state. Clearly a properly balanced blue/green/brown water naval force is in order to deal with the full range of operating environments.

The opinions and views expressed in this post are those of the author alone and are presented in his personal capacity. They do not necessarily represent the views of the U.S. Department of Defense or any of its agencies.

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