From the 1970s the economy stalled while Europe faced numerous social problems. And yet as the cold war ran down the clock, it became gradually clearer that liberal democracy and a market economy mitigated by welfare had won a complete political victory over “actually existing socialism.” At the same time Europe was fully “civilianized”: conscription was abandoned, armies themselves assimilated the values of civilian society and, as the great English military historian Michael Howard has put it, “death was no longer seen as being part of the social contract.”

But life is full of surprises. Sheehan’s book is sprinkled with confident but foolish predictions, like H. N. Brailsford averring in the early summer of 1914 that “there will be no more wars among the six great powers,” or The Economist in September of that year dilating on “the economic and financial impossibility of carrying out hostilities many more months on the present scale.”Just over 70 years later, as cocksure as ever and as wrong, that magazine asserted in 1985 “that nothing much will have changed by the year 2025.” Shortly after those words were published, the Berlin Wall fell, the Soviet empire imploded and savage violence consumed the Balkans, whence so many of Europe’s woes had long stemmed.

Here Sheehan is most sagacious. He sees that the game was up for the Soviet regime the moment Gorbachev disavowed “force and the threat of force,” and he gets the break-up of Yugoslavia right. In late 1991, at the insistence of the German government (itself egged on, one might add, by Serb-bashing right-wing columnists in papers like The Frankfurter Allgemeine), the European Union recognized the sovereignty of Slovenia and Croatia, and then Bosnia, crucially and disastrously before the nationality questions in those territories had been resolved. This encouraged a competitive round of territorial acquisition and ethnic expulsion and “intensified the predatory war being fought by Serbs and Croatians against Bosnia.”

It was of course ludicrous as well as hubristic for Jacques Poos, foreign minister of Luxembourg, to say at this juncture that “the hour of Europe has dawned,” but trans-Atlantic denunciations of European weakness were also misplaced. When the tub-thumpers of Capitol Hill and the op-ed pages were asked 15 years ago what kind of military intervention in the Balkans they had in mind, it turned out to mean American air cover while the Western Europeans provided the P.B.I., as the British Army used to say, the poor bloody infantry, a division of labor that had little appeal in Europe.

What sense does “Mars and Venus” have in the light of the past century, and the price paid by different countries? In 1914-18, 1.3 million Frenchmen (those cheese-eating surrender monkeys) were killed defending their country, which is to say more than twice as many as all the Americans who have died in every foreign war from 1776 until today. There has been much anguish about American casualties in Iraq, where last year was the worst since 2003, with all of 901 deaths. Reading that, the European may reflect silently on the dates Aug. 22, 1914, when 27,000 French soldiers were killed in a day, or July 1, 1916, when 20,000 British troops died.

It isn’t necessary to agree with Evelyn Waugh writing to his friend Graham Greene  “Of course the Americans are cowards. They are almost all the descendants of wretches who deserted their legitimate monarchs for fear of military service”  to see clearly that the United States isn’t a warlike country at all. In many ways it has always been more deeply peaceable in its instincts than ever Europe was.

And is the civilianization of Europe such a bad thing? Although there has been much grumbling about the Bundeswehr’s inadequate contribution in Afghanistan, some of us cannot see it as an occasion for pure regret if the Germans have changed character so drastically. In World War II, the Wehrmacht was unquestionably the best army, man for man and unit for unit, not least against the less ferocious “citizens in uniform” of the British and American Armies. Is that really a cause for British or American shame? When German rearmament began in the 1950s, at American urging, Gustav Heinemann resigned as Adenauer’s interior minister, with the words, “God took arms out of our hands twice; we must not take hold of them a third time.” Was he so wrong?