(Bloomberg View) -- From Ukraine to the South China Sea, the past several years have reminded us that international peace and stability are not givens. The great issues of war and peace, order and disorder, are returning to the forefront of global affairs. My end-of-year reading list is thus made up of books that help us understand the causes and consequences of global upheaval -- and that underscore the exceptional role America has played in holding back the forces of chaos over the past 70 years.
First, there is Thucydides' "History of the Peloponnesian War." This is the granddaddy of them all so far as treatments of war and peace are concerned. It relates the epic struggle between Athens and Sparta in the 5th century BC. The former country was a liberal, commercially oriented maritime power; the latter was a heavily militarized slave society and the dominant land power of ancient Greece. They tangled in a conflict that would last nearly three decades, ravaging both sides and leading to the end of Greece's golden age.
Thucydides narrates the origins and long history of the war, along the way illuminating themes that still figure prominently in the study of international relations: how transitions involving rising and declining powers create immense volatility; the role of fear, honor and self-interest in shaping states' decisions; the idea that the strong do as they will and the weak suffer as they must; the power of ideological cleavages in intensifying geopolitical conflicts between enemies. Above all, Thucydides reminds us that war "proves a rough master": It so often unchains mankind's most basic passions, and occasions destruction on an epic scale.
Some of these ideas have been getting renewed attention lately, with Harvard professor Graham Allison’s discussion of whether America and China can avoid the “Thucydides Trap” in which a rising power and a hegemonic power come to blows. But far better to go back to the original. Thucydides immodestly claimed that his book would be "a possession for all times"; it is indeed an enduring portrayal of the unchanging, elemental aspects of human conflict.
In some ways, a worthy successor to Thucydides is John Mearsheimer’s "The Tragedy of Great-Power Politics," which was originally published in 2001 and updated in 2014. Mearsheimer has gotten a lot of things wrong over the years, particularly when it comes to U.S.-Israel relations and his prescriptions for American grand strategy. But this book is nonetheless one of the most important treatises ever written on international politics.
The core insight is that relations between the great powers are inherently tragic in nature -- that the imperatives of survival and the temptations of aggrandizement invariably lead states to conflict, even if they might prefer a more peaceful path. In a world where there is no supreme authority to enforce order, where states cannot be certain of other states' intentions, and where the penalties for not defending oneself effectively can be catastrophic, all the incentives point to intense, unceasing competition.
Idealists might dream of a world in which the dictates of power politics have been transcended and war is a thing of the past, but Mearsheimer reminds us that states will only enjoy the peace and security they create for themselves. The final chapter of the updated edition -- which painstakingly makes the case for why China’s rise is likely to be profoundly disruptive and perhaps un-peaceful -- should be required reading for anyone who still thinks Beijing will simply become a "responsible stakeholder" in the existing international order.
So how can peace be maintained in such a cut-throat climate? Donald Kagan's classic 1996 work, "On the Origins of War and the Preservation of Peace," offers an answer. Kagan reviews a number of cases -- from the Peloponnesian War to World War II -- in which great-power war did occur, as well as a critical case in which such conflict was averted: the Cuban Missile Crisis. Each of the case studies makes for arresting reading, because the perspicacity of Kagan's insights is matched by the accessibility of his prose.
But the key takeaway is that peace is not, as many people imagine, the natural order of things. Rather, it can be preserved only through extraordinary efforts on the part of powers that wish to maintain the existing order against the inevitable challenges. They must meet threats to international peace and stability early, before the threats gather momentum and the existing system starts to unravel; they must strive to maintain a balance of power that will allow them to restrain or overawe any potential aggressor. Thucydides shows us how brutal great-power war can be. Kagan, one of America's great Thucydides scholars, reminds us that peace is hard work, too.
If Donald Kagan thus helps explain what makes for peace in general, his son, Robert, helps explain the remarkable period of great-power peace that the world has enjoyed since World War II. Robert Kagan's book, "The World America Made," was published several years ago, but is even more timely and relevant today.
The book focuses on the extraordinary role that the U.S. has played in global affairs since World War II -- in promoting free trade, in encouraging the spread of democracy, and above all in suppressing the geopolitical conflicts that had raged in Europe and East Asia for centuries prior. U.S. alliances and forward military deployments restrained potential aggressors such as the Soviet Union; they also stifled historical rivalries between American allies such as France and Germany in Europe, or Japan and South Korea in East Asia.
It would have seemed fantastical to suggest in 1946, after two world wars in the space of a quarter-century, that humanity would subsequently enjoy seven decades of relative great-power peace. But this is precisely the outcome that the U.S. helped bring about. Indeed, Americans have been so successful in playing this stabilizing role, Kagan points out, that today it is all too easy to forget how violent and dangerous the world was before they picked up this burden.
At a time when the international order is once again increasingly in flux, when revisionist powers are testing the contours of the system, and when “the world America made” is under growing strain, Robert Kagan's book -- like all the others mentioned here -- reminds us just how important an education in matters of war and peace truly is.
This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.
Hal Brands is the Henry A. Kissinger Distinguished Professor at the Henry A. Kissinger Center for Global Affairs at Johns Hopkins University's School of Advanced International Studies and a senior fellow at the Center for Strategic and Budgetary Assessments. His latest book is "American Grand Strategy in the Age of Trump."
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