Mayday. By Seth Cropsey, Overlook, 336 pp., $29.95

The American strategist Alfred Thayer Mahan (1840-1914) characterized naval power as “more silent than the clash of arms.” His emphasis on the centrality of this “silent” power in world affairs captured the interest of a young visiting lecturer at the Naval War College in the late 1880s. That lecturer, Theodore Roosevelt, would go on to be president and transform the U.S. Navy into the global force that has underpinned international security and prosperity for a century.

The sort of thinking about naval power that informed Mahan’s and Roosevelt’s work now appears anachronistic. When the U.S. Navy is discussed today, the conversation leaps immediately over strategy to commentary on budgets and the number of ships. Those are aspects of sea power, to be sure, but the ability to command the seas is much more than comparisons with other navies and much more complexly tied to our place in the world. Sea power sets conditions for stable world trade, as some 90% of commerce moves on the oceans. The Navy’s persistent presence far from our shores enables effective diplomacy and provides regional influence without the burdens and sensitivity of deploying ground troops on foreign lands.

In “Mayday: The Decline of American Naval Supremacy,” Seth Cropsey, a former deputy undersecretary of the Navy, argues that the end of unchallenged U.S. supremacy at sea may be closer than American policy makers would like to think. In a well-structured narrative, Mr. Cropsey provides a concise and compelling summary of the evolution of American and other great powers’ application of and dependence on sea power. He chronicles the waxing and waning of that power and the global order that has come with our nation’s ability to command the seas.

Navies aren’t just a whimsical investment of national treasure. Rather, they are an outgrowth of trade and man’s desire to extract resources from the sea, be they fish or natural gas. The relationship of commercial success and naval might is evident in the rise of great powers throughout history—Spain in the 16th century, Holland in the 17th, France in 18th and Great Britain in the 19th. It is likely that today Mahan finds a more devout audience among China’s strategic thinkers than our own. Chinese naval deployments to areas important economically, such as the Southeast Asian sea lanes and the pirate-plagued trade routes in the vicinity of Africa, reinforce Chinese diplomatic and commercial activities. With Beijing so dependent on faraway markets and imports of natural resources, naval power weighs heavily in all its considerations.

China, Mr. Cropsey argues, is on the path to overtake U.S. naval power, with little deliberation in this country about the consequences of such a development. As Mr. Cropsey warns, reducing the number of U.S. ships “accelerates the decline of American sea power, unintentionally adding strategic weight to Beijing’s naval buildup, and more important, to China’s rise to dominance in Asia. Politicians have not faced this basic question of strategy.”

The last transfer of sea power was between nations, Great Britain and the U.S., that shared political values and commercial philosophies and saw eye-to-eye on freedom of navigation in international waters. It was a seamless transition for the international order at the time. What will be the effect among our allies and like-minded partners should U.S. sea power wane, our global naval presence diminish and China replace the U.S. as the guarantor of international commerce and maritime security? As Mr. Cropsey says, “the signs point to a change in power in the western Pacific,” a region of great importance to our future prosperity.

With its 286 ships, the U.S. Navy is now smaller than it was in 1917, when it boasted 342. The number is stuck, and the trend spans the administrations of both parties. We have spent heavily on our wars in Iraq and Afghanistan, and the U.S. Navy, which is central to our long-term strategic interests, languishes. Navies, unlike armies, take time to build—why the framers of our Constitution wrote of the imperative to “provide and maintain a Navy,” as opposed to the need to “raise and support an Army.”

“Mayday” provides an insider’s view into the many ills of the Navy’s planning and budgeting system. These range from low and unsteady quantities of ship orders; to the trade-offs between building a few cutting-edge ships and more ships less technologically complex; to the ever increasing “contractual, statutory and regulatory” burdens on the Navy. The latter include a requirement for new paints that emit fewer toxins in shipbuilding; compliance adds an estimated $16 million to the price of an aircraft carrier. But “Mayday” doesn’t address forcefully enough how diminishing procurement budgets will be further eroded by rapidly rising personnel costs and inefficiencies within the procurement process itself.

Mr. Cropsey offers some good recommendations to adjust the size and makeup of the Navy. He wisely advocates that “the most advanced technology should bow to numbers” and argues for pursuing unmanned systems to achieve “decreased cost and increased surveillance and combat power.” Yet some of his suggestions fall short, in that they assume a linear relationship between cost and reduced ship size. The inconvenient truth is that a ship that is half the size doesn’t cost half as much. Deploying more small ships is appealing, but to get to areas of interest such as the Middle East, the Western Pacific and the Indian Ocean we must cross vast waters and remain present for extended periods. Size, speed, endurance and lethality matter greatly, especially when forward bases can’t be assured at a time when foreign populations are prickly about sovereignty.

But “Mayday” is extremely timely, reminding us that security and prosperity are inextricably linked to sea power. As John F. Kennedy said half a century ago: “Control of the sea means security. Control of the sea means peace. Control of the sea can mean victory.”

Adm. Roughead, a former chief of naval operations, is a fellow at the Hoover Institution.