Yet another cause of war, and often an excuse for it, is a sense that, as Macmillan points out, the nation or the ruler’s “honor” has somehow been impugned, whether as a result of an immediate or long-standing affront. She offers an example of the former in Britain’s decision to go to war because the Spanish had cut off Captain Robert Jenkins’ ear. Actually, she notes, the war was about control of trade in the Caribbean. She might have added that the cry to “Remember the Maine” was as much about the American desire to rid the Caribbean of its Spanish presence as about the supposed sinking of the battleship. An example of a more recent vintage was Argentina’s mid-1982 occupation of the Falkland Islands. The year 1983 would have marked 150 years since the British first occupied the islands; as Lawrence Freeman and Virginia Gamba-Stonehouse observed in their masterful account of that war, “The symbolic importance of this anniversary meant that there would be pressure within Argentina demanding strong action by the government of the day in Buenos Aires.” 

Often even more than wars between states, civil wars can be especially brutal. Even when one side nominally has prevailed, the losing side’s bitterness can linger for decades, or even longer. As Macmillan rightly points out, “We feel a particular horror at civil wars both because they rip apart the bonds that hold societies together and because they are so often marked by unrestrained violence toward the other side.” The lingering resentment of the American South, which has played out in presidential elections since 1964 and was a factor both in Donald Trump’s 2016 campaign and his fight for re-election in 2020, is a notable case in point. 

It is true, as Macmillan notes, that “The American Civil War probably had more casualties than all other American wars combined.” Yet her focus on Western warfare overlooks the Taiping Rebellion, which actually was a civil war between rival claimants to power. That war, which overlapped with the American Civil War, lasted nearly four times as long and resulted in as many as seventy million dead, more than twenty times the total of American casualties on both sides. Macmillan also notes that it was the Romans who first came up with the notion of “civil war,” though the Book of Judges recounts the near extermination of the tribe of Benjamin by the other Hebrew tribes centuries before Marius and Sulla contested the leadership of Rome.

WHEN MACMILLAN turns to what she terms the “ways and means” of warfighting, she asserts that “how societies fight wars and the weapons they use affect and are affected by their values, their beliefs and ideas, and their institutions, their culture in the broadest sense.” She adduces considerable historical backing for her observations about the impact of culture on those who would wage war. She points to warrior-societies ranging from ancient Sparta to Prussia. And she posits that cultures that venerate war look down upon cultures that do not: The Romans considered Carthaginians to be effeminate and the British took the same dim view of Bengalis while admiring Gurkhas and others whose war-fighting abilities they put down to the cooler climates of their homelands. She adds, “How groups of humans contemplate and plan for wars is also affected by their … geography.” America was blessed by the protection that great oceans afforded it; it could rely on relatively small land forces. Britain, surrounded by water, could do the same, assigning its highest military priority to the Royal Navy. Germany and Russia, with no such protection, accorded pride of place to their armies. Up to a point her observations apply today: most states on the Asian mainland, for example, including China (despite her growing maritime capability), assign budgetary priority to their armies; an island nation like Japan does so for its navy.

It is certainly true that, as Macmillan asserts, “culture, technology and war are … interdependent” in the sense that “war pushes ahead the development of technology but it also adapts what is already there.” This was the case in ancient times and is true today. For example, the U.S. Defense Department has sought in a variety of ways to exploit Silicon Valley’s technological breakthroughs—though the commercial hi-tech sector is notably reluctant to work with government. 

It is equally the case that Americans’ enterprising spirit has spurred the country’s advances in artificial intelligence, machine learning, hypersonics, 5G, and other emerging technologies. The gung-ho attitude that pervades Israeli entrepreneurial society likewise has resulted not only in the Jewish state’s emergence as a “start-up nation,’ but has also transformed its military into a regional powerhouse. Yet China, with a very different culture and political system, has actually outpaced the United States in several of these technologies, and not only because it has copied or stolen them. Similarly, Russia’s advances, especially in hypersonics, are very much indigenous, though its society is once again under the thumb of a harsh authoritarian regime.

Moreover, the tools of modern war, whatever their origins, are fundamentally different from those Macmillan cites in her chapter on “modern” war. Just as she rightly contrasts the nature of warfare in ancient times from that of World War I, and that of the Great War from that of World War II, so too will future wars differ from those of even the recent past. It is unfortunate that Macmillan reserves for her brief final chapter her very cogent observations about the revolutionary nature of what is truly modern warfare.

Macmillan’s discussion of the nature of “modern” war, like that of “modern” weapons, likewise tends to focus more on World War I and the wars that preceded it than on the impact of future conflicts on both combatants and the societies that support them. It is true that beginning with Napoleonic France, through World Wars I and II, and most recently America’s wars in Afghanistan and Iraq, “modern war [has] last[ed] longer [and] cost more.” Since the end of the Vietnam War, however, conflict has not, as Macmillan asserts, “demand[ed] more of society.” When the United States went to war in Afghanistan, President George W. Bush instructed the American people, “they have got to go about their business.” He did not change his position when the United States invaded Iraq two years later. Americans were not asked to buy war bonds to finance the two wars that have cost them hundreds of billions of dollars, and, if veterans’ benefits are included, will cost billions more over the next decades.

Moreover, wars are once again the preserve of a professional class as volunteer militaries replace those that depend on conscription. Macmillan’s observation that “it has almost always been the young men who volunteer or are taken first for war” is now only partially accurate. Young men volunteer, but they are heavily recruited. And not just men. Women volunteer and they too are recruited. And both young men and women in the military, at least in the American military, have families with small children. Indeed, one of the major causes of pressure on the American defense budget is the proliferation of benefits both to entice young men and women, including those with families, to join the military and then to re-enlist.

Modern war, at least for American forces, is changing in another respect. Macmillan rightly notes that “a strong sense of comradeship and a willingness to follow orders, which make men fight and endure together, can lead to systematic organized cruelty and evil.” After all, Adolf Eichmann’s defense when he was tried for mass murder was that he was “only following orders.” The Eichmann defense is no longer operative, at least in the American military. Instead, it is charged to ignore illegal orders, such as torture. Moreover, in the wake of the Lafayette Square incident and his subsequent defeat in the 2020 presidential election, military leaders agonized over the question of how to respond to an order from President Trump that they might deem to be illegal, such as an unprovoked nuclear strike. 

If militaries and their weapons have undergone marked change in the past several decades, the outsized role of the media in influencing public opinion in support of, or opposition to, war has not changed very much since the mid-1800s. To paraphrase Macmillan, “war is good for sales.” Moreover, just as the media has long been, and still can be, a forceful voice in support for a war, it can also render a conflict increasingly unpopular. Walter Cronkite’s televised opposition to the Vietnam War helped turn the country against it. And, as Macmillan rightly contends, once popular opinion turns against a war, it becomes increasingly difficult for a government to sustain it. America’s Vietnam, the USSR’s and America’s respective wars in Afghanistan, the war in Iraq, and Israel’s withdrawal from southern Lebanon all support her point.

Macmillan is also on the mark in arguing that “governments and their military have learned to play the game of manipulating public opinion too.” She incorrectly asserts, however, that “although the US military allowed reporters extraordinary access in Vietnam, it drew the conclusion that it must never make that mistake again. In both wars with Iraq the media were tightly controlled and managed.” To the contrary, despite its difficulties with the media in Vietnam, the military decided to risk giving reporters free rein in both Iraq wars, and has since concluded that it made the correct decision. While some older reporters (and they were almost all men) who had covered the Vietnam War were distrustful of the military’s operations in Iraq, younger ones were far less so. Moreover, members of the press who were “embedded” with particular units in Iraq were free to join other units, and some certainly did so, even joining up with the special operations forces.