By George Friedman

It has now been four years since the fall of Baghdad concluded the U.S. invasion of Iraq. We have said much about the Iraq war, and for the moment there is little left to say. The question is whether the United States will withdraw forces from Iraq or whether it will be able to craft some sort of political resolution to the war, both within Iraq and in the region. Military victory, in the sense of the unfettered imposition of U.S. will in Iraq, does not appear to us a possibility. Therefore, over the next few months, against the background of the U.S. offensive in Baghdad, the political equation will play out. The action continues. The analysis must pause and await results.

During this pause, we have been thinking about some of the broader questions involved in Iraq -- and about the nature and limits of American military power in particular. We recently considered the purpose of U.S. wars since World War II in our discussion of U.S. warfare as strategic spoiling attack. Now we turn to another dimension of U.S. military power -- the U.S. Navy -- and consider what role, if any, it plays in national security at this point.

Recent events have directed our attention to the role and limits of naval power. During the detention of the 15 British sailors and marines, an idea floated by many people was that the United States should impose a blockade against Iran. The argument was driven partly by a lack of other options: Neither an invasion nor an extended air campaign seemed a viable alternative. Moreover, the United States' experience in erecting blockades is rich with decisive examples: the Cuban missile crisis, barring Germany's ability to trade during World War II or that of the American South during the Civil War. The one unquestionable military asset the United States has is its Navy, which can impose sea-lane control anywhere in the world. Finally, Iran -- which is rich in oil (all of which is exported by sea) but lacks sufficient refinery capacity of its own -- relies on imported gasoline. Therefore, the argument went, imposing a naval blockade would cripple Iran's economy and bring the leadership to the negotiating table.

Washington never seriously considered the option. This was partly because of diplomatic discussions that indicated that the British detainees would be released under any circumstances. And it was partly because of the difficulties involved in blockading Iran at this time:

1. Iran could mount strategic counters to a blockade, either by increasing anti-U.S. operations by its Shiite allies in Iraq or by inciting Shiite communities in the Arabian Peninsula to unrest. The United States didn't have appetite for the risk.

2. Blockades always involve the interdiction of vessels operated by third countries -- countries that might not appreciate being interdicted. The potential repercussions of interdicting merchant vessels belonging to powers that did not accept the blockade was a price the United States would not pay at this time.

A blockade was not selected because it was not needed, because Iran could retaliate in other ways and because a blockade might damage countries other than Iran that the United States didn't want to damage. It was, therefore, not in the cards. Not imposing a blockade made sense.

The Value of Naval Power

This raises a more fundamental question: What is the value of naval power in a world in which naval battles are not fought? To frame the question more clearly, let us begin by noting that the United States has maintained global maritime hegemony since the end of World War II. Except for the failed Soviet attempt to partially challenge the United States, the most important geopolitical fact since World War II was that the world's oceans were effectively under the control of the U.S. Navy. Prior to World War II, there were multiple contenders for maritime power, such as Britain, Japan and most major powers. No one power, not even Britain, had global maritime hegemony. The United States now does. The question is whether this hegemony has any real value at this time -- a question made relevant by the issue of whether to blockade Iran.

The United States controls the blue water. To be a little more precise, the U.S. Navy can assert direct and overwhelming control over any portion of the blue water it wishes, and it can do so in multiple places. It cannot directly control all of the oceans at the same time. However, the total available naval force that can be deployed by non-U.S. powers (friendly and other) is so limited that they lack the ability, even taken together, to assert control anywhere should the United States challenge their presence. This is an unprecedented situation historically.

The current situation is, of course, invaluable to the United States. It means that a seaborne invasion of the United States by any power is completely impractical. Given the geopolitical condition of the United States, the homeland is secure from conventional military attack but vulnerable to terrorist strikes and nuclear attacks. At the same time, the United States is in a position to project forces at will to any part of the globe. Such power projection might not be wise at times, but even failure does not lead to reciprocation. For instance, no matter how badly U.S. forces fare in Iraq, the Iraqis will not invade the United States if the Americans are defeated there.

This is not a trivial fact. Control of the seas means that military or political failure in Eurasia will not result in a direct conventional threat to the United States. Nor does such failure necessarily preclude future U.S. intervention in that region. It also means that no other state can choose to invade the United States. Control of the seas allows the United States to intervene where it wants, survive the consequences of failure and be immune to occupation itself. It was the most important geopolitical consequence of World War II, and one that still defines the world.

The issue for the United States is not whether it should abandon control of the seas -- that would be irrational in the extreme. Rather, the question is whether it has to exert itself at all in order to retain that control. Other powers either have abandoned attempts to challenge the United States, have fallen short of challenging the United States or have confined their efforts to building navies for extremely limited uses, or for uses aligned with the United States. No one has a shipbuilding program under way that could challenge the United States for several generations.

One argument, then, is that the United States should cut its naval forces radically -- since they have, in effect, done their job. Mothballing a good portion of the fleet would free up resources for other military requirements without threatening U.S. ability to control the sea-lanes. Should other powers attempt to build fleets to challenge the United States, the lead time involved in naval construction is such that the United States would have plenty of opportunities for re-commissioning ships or building new generations of vessels to thwart the potential challenge.

The counterargument normally given is that the U.S. Navy provides a critical service in what is called littoral warfare. In other words, while the Navy might not be needed immediately to control sea-lanes, it carries out critical functions in securing access to those lanes and projecting rapid power into countries where the United States might want to intervene. Thus, U.S. aircraft carriers can bring tactical airpower to bear relatively quickly in any intervention. Moreover, the Navy's amphibious capabilities -- particularly those of deploying and supplying the U.S. Marines -- make for a rapid deployment force that, when coupled with Naval airpower, can secure hostile areas of interest for the United States.

That argument is persuasive, but it poses this problem: The Navy provides a powerful option for war initiation by the United States, but it cannot by itself sustain the war. In any sustained conflict, the Army must be brought in to occupy territory -- or, as in Iraq, the Marines must be diverted from the amphibious specialty to serve essentially as Army units. Naval air by itself is a powerful opening move, but greater infusions of airpower are needed for a longer conflict. Naval transport might well be critically important in the opening stages, but commercial transport sustains the operation.

If one accepts this argument, the case for a Navy of the current size and shape is not proven. How many carrier battle groups are needed and, given the threat to the carriers, is an entire battle group needed to protect them?

If we consider the Iraq war in isolation, for example, it is apparent that the Navy served a function in the defeat of Iraq's conventional forces. It is not clear, however, that the Navy has served an important role in the attempt to occupy and pacify Iraq. And, as we have seen in the case of Iran, a blockade is such a complex politico-military matter that the option not to blockade tends to emerge as the obvious choice.

The Risk Not Taken

The argument for slashing the Navy can be tempting. But consider the counterargument. First, and most important, we must consider the crises the United States has not experienced. The presence of the U.S. Navy has shaped the ambitions of primary and secondary powers. The threshold for challenging the Navy has been so high that few have even initiated serious challenges. Those that might be trying to do so, like the Chinese, understand that it requires a substantial diversion of resources. Therefore, the mere existence of U.S. naval power has been effective in averting crises that likely would have occurred otherwise. Reducing the power of the U.S. Navy, or fine-tuning it, would not only open the door to challenges but also eliminate a useful, if not essential, element in U.S. strategy -- the ability to bring relatively rapid force to bear.

There are times when the Navy's use is tactical, and times when it is strategic. At this moment in U.S. history, the role of naval power is highly strategic. The domination of the world's oceans represents the foundation stone of U.S. grand strategy. It allows the United States to take risks while minimizing consequences. It facilitates risk-taking. Above all, it eliminates the threat of sustained conventional attack against the homeland. U.S. grand strategy has worked so well that this risk appears to be a phantom. The dispersal of U.S. forces around the world attests to what naval power can achieve. It is illusory to believe that this situation cannot be reversed, but it is ultimately a generational threat. Just as U.S. maritime hegemony is measured in generations, the threat to that hegemony will emerge over generations. The apparent lack of utility of naval forces in secondary campaigns, like Iraq, masks the fundamentally indispensable role the Navy plays in U.S. national security.

That does not mean that the Navy as currently structured is sacrosanct -- far from it. Peer powers will be able to challenge the U.S. fleet, but not by building their own fleets. Rather, the construction of effective anti-ship missile systems -- which can destroy merchant ships as well as overwhelm U.S. naval anti-missile systems -- represents a low-cost challenge to U.S. naval power. This is particularly true when these anti-ship missiles are tied to space-based, real-time reconnaissance systems. A major power such as China need not be able to mirror the U.S. Navy in order to challenge it.

Whatever happens in Iraq -- or Iran -- the centrality of naval power is unchanging. But the threat to naval power evolves. The fact that there is no threat to U.S. control of the sea-lanes at this moment does not mean one will not emerge. Whether with simple threats like mines or the most sophisticated anti-ship system, the ability to keep the U.S. Navy from an area or to close off strategic chokepoints for shipping remains the major threat to the United States -- which is, first and foremost, a maritime power.

One of the dangers of wars like those in Iraq and Afghanistan is that they soak up resources and intellectual bandwidth. It is said that generals always fight the last war. Another way of stating that is to say they believe the war they are fighting now will go on forever in some form. That belief leads to neglect of capabilities that appear superfluous for the current conflict. That is the true hollowing-out that extended warfare creates. It is an intellectual hollowing-out.

The Limitations and Necessity of Naval Power