Waterworld.

• Author: Bakshian, Aram

David Abulafia, The Boundless Sea: A Human History of the Oceans (New York: Oxford University Press, 2019), 912 pp., $39.95.

Much as we like to pat ourselves on the back about human progress, lots--if not most--of it has been the product of chance observation and unintended consequences. Observing a moldy piece of bread triggers a eureka moment in the development of penicillin; a mundane ride on a trolley helps Albert Einstein conceptualize his theory of relativity; the efficacy of Vitamin C in preventing scurvy is stumbled upon by eighteenth-century British naval officers who notice that a regular supply of lime juice avoids outbreaks of the disease on long ocean voyages (earning British sailors their traditional nickname, "Limeys"). The list goes on and on.

Of all the fields of human progress, none owes more to unintended consequences than global exploration. The great American naval historian and Columbus biographer, Samuel Eliot Morison, summed it up admirably when he wrote--half in earnest, half in jest--that:

America was discovered accidentally by a great seaman who was looking for something else; when discovered, it was not wanted; and most of the exploration for the next fifty years was done in the hope of getting through or around it. America was named after a man who discovered no part of the New World. History is like that, very chancy. In The Boundless Sea: A Human History of the Oceans, Cambridge historian David Abulafia offers a majestic narrative of mankind's incredible, sea-born drive toward global discovery and interconnection, a voyage beginning in prehistoric times and lasting all the way up to the twenty-first century. From the beginning, the very seas that separate us have also served as a liquid bridge, first between neighboring islands but ultimately between continents and hemispheres, as mankind mastered navigation and gradually discovered the Earth's true size and shape.

Even today, in the age of jet transport and space exploration, the seas are still the broadest thoroughfare for global commerce, and naval strength still plays a critical part in the international balance of power. In a globalized age, mastery of the seas is, if anything, more important than ever. America's place as a superpower is more reliant than ever on its ability to keep seaways open and to use its naval power to deploy air and land forces wherever and whenever needed.

As it happens, mastery of the seas for at least three centuries has been an Anglo-Saxon monopoly, often challenged but never broken. While the British standing army was usually a relatively small, neglected fighting force compared to its main continental rivals--France in the eighteenth and early nineteenth centuries and Germany in the late nineteenth and early twentieth centuries--the Royal Navy remained the undisputed ruler of the waves throughout the period. On the whole, this has proven to be a good thing.

British naval power was the key to thwarting the attempts of Louis XIV and his autocratic Bourbon successors, and a Napoleonic military dictatorship after them, to impose their will on the rest of Europe. With the decline of France and the rise of a unified Germany dominated by Prussian militarists, the Royal Navy's continued domination of the seas was essential to Allied victory in World War I. World War II represented an important transition--an Anglo-Saxon naval condominium. The still-dominant but overstretched naval power of Great Britain was reinforced by the rising naval power of the United States, where the building of a vast, "two-ocean" navy had begun earlier in the century under President Theodore Roosevelt. By war's end, an exhausted Britain had begun its imperial recessional, which included a diminished naval presence. The oceanic torch was passed from one Anglo-Saxon partner to the other.

Alfred Thayer Mahan's description of the role of the Royal Navy in stopping Napoleon from dominating the rest of Europe could be updated to describe the role of American naval power in helping to topple Hitler and then containing Soviet...