Massive dreadnaughts belching fire and smoke in a line of battle. Battlecruisers racing at high speed. The German High Seas Fleet versus the British Grand Fleet. These are what most readers envision when they think of naval surface combat[1] during the First World War. The battle of Jutland, the largest single concentration of combatants in such an engagement, has achieved near-mythic status in the annals of naval warfare. But, beyond a few other major battles (e.g., Dogger Bank and Heligoland Bight in the North Sea), the war at sea in 1914–18 is recalled as insignificant and indecisive compared to the many devastating land battles of the war. The authors of Clash of Fleets demonstrate that the war at sea was in fact critical to the ultimate outcome of the conflict.

In their highly readable, long overdue account, historians Vincent O'Hara and Leonard Heinz offer a refreshing, thorough, and corrective examination of 144 surface naval engagements of the First World War in six distinct theaters: the North, Baltic, Black, Mediterranean, and Adriatic seas, as well as non-European waters. Readers will learn that, rather than a contest between only British and German dreadnaughts in the North Sea, the Great War was truly a world war at sea as well as on land.

Beyond compiling, cataloging, and explaining the war's naval engagements from August 1914 to October 1918, the authors discuss in detail why the war on the surface turned out as it did. Much like the war on land, it did not evolve as strategists had anticipated. The decisive naval battle predicted by Alfred Thayer Mahan never really took place. As colossal and memorable as Jutland was, it was far from conclusive. Despite its tactical victory, the German fleet remained bottled up in its ports for the remainder of the war, all but ceding control of the North Sea to the British. Jutland symbolized all that had been misforeseen before the war: "In the subsequent trial by fire some systems did not work as expected, some were not used as anticipated, and others established an unexpected importance" (2).

The first of the book's seven chapters, "The Fleets," specifies the various warship types, their capabilities, weapons, and technologies. Chapters 2–6[2] sketch the situation at the beginning of each year of the war and then catalog each naval engagement of that year. The final chapter, "Summing Up," states the authors' conclusions and assesses the individual navies' conduct of the war. The authors stress that each theater posed its own distinct challenges, but in all of them "Sea power played a vital role ... and surface warfare was fundamental to its application" (2).

A great strength of the book is its lucid prose style. Even when discussing details of gunnery, torpedo design, and naval tactics, the authors avoid technical jargon. Still more importantly, they clarify the strengths, weaknesses, and strategies of the seven belligerent European navies: specifically, Britain's Royal Navy, Germany's Kaiserliche Marine, Austria-Hungary's Kaiserliche und Königliche Kriegsmarine, the Ottomans' Osmanli Donanmasi, France's Marine Nationale, Italy's Regia Marina, and Russia's Rossiiski Imperatorski Flot. The US Navy is not included, since it took part only in the U-boat war and not in significant surface-fleet engagements. The discussion of the Italian, French, Russian, and Turkish navies is most welcome and illuminating, as their place in the naval history of war has long been overlooked.

As mentioned, the authors stress the surprising results of the war at sea: "Naval surface combat commonly evokes an image of battleships proceeding majestically in column with massive guns roaring in great gouts of smoke and fire—and it could be like this, but not very often" (2). Instead, naval actions in the various theaters were more varied and often more mundane than had been anticipated. As the authors make clear, it was not only—or even mainly—the dreadnaughts, but lowly minesweepers that became the true "arbiters of naval power" by 1918 (275).

The outsized role of minelayers and minesweepers in the war at sea could not have been foreseen by any admiralty in 1914. These vessels did unglamorous but vital work. During the fifty-one months of the conflict, Great Britain laid over 128,000 mines, the United States 57,000, the Russians 52,000, and the Germans 43,000. Removing these deadly and unforgiving devices became an urgent priority. Mines cost the British forty-six warships and over 225 auxiliaries during the war. The British struggle with minesweeping gave the Royal Navy an expertise it retains to this day.

Its succinct yet well researched and richly informative summaries of individual battles lie at the heart of the book. A typical example is the authors' vivid account of the now forgotten battle of Gotland (2 July 1915). In calm but foggy weather conditions, a small Russian cruiser force met a German minelaying flotilla near Gotland Island in the central Baltic Sea. The Russians had the advantage in numbers and inflicted considerable damage on the German force. But the victory was incomplete, because R. Adm. M.K. Bakhirev fought too conservatively and let some German units escape through the fog. The authors register every detail of the battle, including weather, force formations, tactics, and casualties.

The final chapter, "Summing Up" offers some intriguing conclusions: most naval engagements of the war were unexpected and unwanted, few were directed against precise targets, and ships were rarely sunk or heavily damaged. Naval commanders, especially of the German High Seas Fleet, were so cautious by war's end as to rule out nearly any aggressive use of their fleets. Hence, paradoxically, though the warships of the Entente powers were rated lower on a ship-to-ship basis than their Central Powers opponents, only the Royal Navy came close to achieving its strategic goals, regardless of its tactical ineptitude. And, despite its poor historical reputation, the ill-maintained Russian Navy in both the Baltic and Black Seas fought bravely until the 1917 revolution.

Clash of Fleets is not a narrative history, but a meticulous catalogue of not only the battles, but also the ships and naval technology of World War I. Although most of the archival research for it centered on English-language sources, such as battle reports from the British National Archives, German, Italian, and French primary sources were also used. The book should now be the standard resource for anyone seeking a thorough and accessible account of naval combat during the Great War.