Why War Still Surprises

War and Power
Who Wins Wars―and Why
by Phillips Payson O’Brien
PublicAffairs, 276 pp., $30

WHY DO COUNTRIES WIN OR LOSE wars? With a major war raging in Europe, and a possible conflagration with China looming in the decade ahead, no question is of more urgent importance.

Phillips O’Brien, an American professor of strategic studies at the University of St. Andrews in Scotland, argues that an answer can be derived by studying the wars of the twentieth and twenty-first centuries. O’Brien, a prolific military historian, has been a close observer of the Russian–Ukrainian war, writing about it on his invaluable Substack, and is now the author of War and Power, a book that promises a new “methodology” for understanding how states interact in armed conflict and what makes them “strong” or “weak.”

Before the full-scale Russian invasion of Ukraine in February 2022, the consensus among Western military analysts was that it would be a cakewalk. The U.S. government was making plans to spirit Ukrainian President Volodymyr Zelensky out of the country to safety in the West. In a classified briefing to Congress shortly before the tanks rolled across the border, then-Chairman of the Joint Chiefs of Staff Gen. Mark Milley predicted that Kyiv would fall in 72 hours, and that Ukraine would suffer 15,000 battle deaths compared to a Russian total of 4,000.

Such pessimism was by no means confined to the Pentagon. It was widespread in think tanks and in the analytic community that was advising the U.S. government. Policy choices flowed from such dire predictions. It would be futile for the United States to aid Ukraine with weapons, the thinking went, because the Russian onslaught would be so rapid and devastating. Samuel Charap, a top analyst at the RAND Corporation, argued that the United States could “do nothing” to alter the outcome. And as O’Brien notes, this was “no one-off. It was a vision of Russian power and Ukrainian weakness that had been used for years to argue against providing Ukraine with modern weaponry—on the assumption that Ukrainian conventional resistance against the great power of Russia was doomed.” (O’Brien dissented from this analytic consensus at the time, noting the weaknesses of the Russian military and Ukraine’s underappreciated strengths.)

O’Brien traces such colossal misjudgment in part to the widely embraced concept of “great powers” and the blithe assumption that Russia was one of them, which he closely ...