Here's a thought experiment: would America build the U.S. Navy currently plying the seven seas if it were starting from scratch? Color me skeptical. If not, what kind of navy would it build, and how can we approximate that ideal in light of budgetary constraints, a slew of legacy platforms that can't simply be scrapped and replaced, and an organizational culture and history that frown on revolutionary change?

For the idea behind this exercise, a tip of the hat goes to Shawn Brimley and Paul Scharre of the Center for a New American Security or CNAS, who ran an item over at Foreign Policy last May wondering how the United States would reboot the armed forces as a whole. Brimley and Scharre dangle their query out there with a few remarks about organizational wiring diagrams and personnel policy. They hint at answers without quite giving them. They want to start a rumble within officialdom. In a novus ordo seclorum, would we create, say, a separate U.S. Air Force, or institute recruitment and retention policies reminiscent of conscription? Such matters are worth pondering.

Last week, writing in a similar vein, Washington Post columnist and sometime naval enthusiast George Will asked what kind of navy the nation needs, and wants. That sounds like a technical question. And it is -- in part. Is the U.S. Navy outfitted with the right types and numbers of ships, aircraft, and armaments?

Yet Will cuts to the heart of the matter. At bottom this is less a question about gadgetry or high-seas tactics than about national purposes and power. Nations, that is, amass military power to fulfill larger purposes. Martial strength helps advance their interests, ward off danger, and uphold their ideals. But does a listless American republic, "demoralized by squandered valor in Iraq and Afghanistan, and dismayed in dramatically different ways by two consecutive commanders in chief," even want to project power overseas?

If so, where, and to what ends? Today, maintains Will, "cascading dangers are compelling Americans to think afresh about something they prefer not to think about at all -- foreign policy. What they decide that they want will define the kind of nation they want the United States to be. This abstract question entails a concrete one: What kind of navy do Americans want?"

Good question. There's a canned quality to what-if exercises like this one. Two basic approaches come to mind. One, there's the tabula rasa. You could posit that the United States is only now rising to regional or world power, and thus is making itself a sea power for the first time. Such a scenario would be a throwback to 1883, when the nation started constructing its first steam-driven battle fleet. Americans could start from first principles, asking themselves what they wanted to accomplish in the world and what kind of naval might their republic needed to accomplish it.

Or, two, you could stipulate that the United States somehow made itself into the world power it is, blessed and burdened by its current array of foreign alliances and commitments, without ever having built an imposing navy to bind such arrangements together. The challenge in this unlikely scenario would be to field a fleet able to uphold commitments to Japan, Australia, NATO, and so forth. The demands of these two constructs are starkly different. For the fun of it, and to avoid a War and Peace-length discourse -- a zero-based look at U.S. foreign policy would consume page after page -- let's go with the latter. What kind of navy should Washington build to discharge today's commitments if starting afresh?

To further simplify the problem, let's accept the geopolitical assessment set forth in the 2007 U.S. Maritime Strategy, titled A Cooperative Strategy for 21st Century Seapower. In the strategy the chieftains of the U.S. Navy, Marine Corps, and Coast Guard pronounce the Western Pacific and greater Indian Ocean the primary theaters for U.S. marine endeavor. They pledge to stage credible combat power in the Indo-Pacific for the foreseeable future, using forward-deployed forces to execute a variety of missions. Enforcing freedom of the seas and skies in peacetime, deterring war or winning it, and rendering humanitarian or disaster relief rank high on the sea services' to-do list.

How to proceed? When contemplating grand enterprises, you seldom go wrong starting with Carl von Clausewitz. Clausewitz urges statesmen and commanders to take a tour d'horizon before picking up the sword. To "discover" how many and what type of resources they need to marshal, they need to evaluate the adversary's and their own political aims. What does each belligerent want, and how much does it want it? Strategic overseers should survey the opponent's "strength and situation," appraising everything from geography to military potential to morale. They should "gauge the character and abilities" of the opponent's government and people, and of their own. And they should evaluate the "political sympathies" of third parties, estimating the likely impact of military action on these prospective allies, enemies, or bystanders.

Clausewitz's discovery process is meant for discrete conflicts, but it's a serviceable template for long-term strategy as well. Applied to the Indo-Pacific rimlands, who are the likely competitors, what are their long-term interests and aspirations, and how much are they prepared to invest in fulfilling these aspirations? How can Washington sway them in favor of American policy? What advantages and liabilities does prospective antagonists' offshore geography present, how much and what type of military potential do they boast, and is their warmaking potential likely to wax, wane, or stagnate over time? Are their people and government well suited to long-term strategic competition? And what impact will the competition have on third parties? Will it help the United States firm up its alliances or woo new partners? Or will it erode ties in the region?

Sizing up the strategic surroundings, then, represents the beginning of wisdom. Now let's neck down to the operational and hardware levels. How can a reinvented U.S. Navy achieve its goals amid Indo-Pacific surroundings? For insight let's ask that scion of Edwardian England, sea-power theorist Julian S. Corbett. Corbett partitions navies into the "battle fleet," "cruisers," and the "flotilla." The battle fleet dukes it out with enemy fleets for command of vital waters. Thrashing the enemy frees the cruisers and flotilla -- swarms of lighter, less heavily armed, cheaper craft -- to fan out in large numbers, controlling seagoing traffic at important junctures on the map. Command also empowers a navy to blockade enemy shores, land troops, or otherwise project force from the sea. These too are jobs for cruisers and the flotilla.

And they're the crucial jobs. Harnessing the sea for our purposes while keeping enemies from interfering is the point of maritime strategy. Battle, then, is only an enabler in marine warfare -- not an end in itself. "Capital ships" constituting the battle fleet thus occupy a curious place in navies. They enjoy most of the sex appeal, festooned as they are with radars, missiles, and guns. And their efforts are indispensable to success. Enemy sea power does have to be expelled from the expanses that matter, or at least reduced to near-impotence. But at the same time Corbett insists that the battle line's chief function is to protect unsexy cruisers and flotilla ships at their "special work." Though celebrated in legend and song, then, fleet engagements are merely a means to that happy end. Savvy commanders refuse to fight Trafalgar- or Leyte-like actions for their own sake.

This was true in Corbett's day, but what about our own? Seeking out the enemy fleet for a major action at the outset of a conflict -- Corbett's preferred method for settling affairs -- may avail a dominant navy little in today's strategic setting. That's because incapacitating or sinking an enemy fleet no longer represents a sure route to success, as it did during the age of Corbett a century ago. No longer is sea power all about fleets. For instance, arsenals of anti-ship missiles and aircraft can strike hundreds of miles from a local defender's coasts -- shaping events on the high seas even if no surface fleet gets underway. Even if our hypothetical U.S. Navy, say, knocks China's shiny new fleet out of a conflict, American task forces must still operate under the shadow of shore-based sea power. Disabling Chinese airfields or mobile anti-ship-missile batteries threatens to be harder and more exasperating than fighting a concentrated fleet.

Corbett's Royal Navy never faced barrages of Imperial German anti-ship ballistic or cruise missiles lofted its way. The Corbettian playbook for maritime warfare remains relevant -- but naval commanders should flip to the pages in his book Some Principles of Maritime Strategy that explore how to start campaigns from a position of weakness. If it proves impossible to win command of the commons through a decisive encounter at the outset, what then? Well, a U.S. Navy optimized for an anti-access environment would deploy assets to eliminate the opponent's navy (or, second best, bottle it in port) while trying to nullify the land-based component of enemy sea power. It would deny the opponent his goals as a first step.