Historian Margaret MacMillan skyrocketed to global prominence nearly two decades ago with the publication of “Paris 1919,” a riveting and authoritative account of the hugely consequential peace conference following World War I.  Since then, she has written about the causes of World War I, President Richard Nixon’s 1972 trip to China and the uses and abuses of history.

In “War: How Conflict Shaped Us,” MacMillan deploys her formidable skills of narration and analysis to assess one of the most mysterious aspects of the human experience: war.

“War is not an aberration, best forgotten as quickly as possible,” she writes. “Nor is it simply an absence of peace which is really the normal state of affairs. If we fail to grasp how deeply intertwined war and human society are — to the point where we cannot say that one predominates or causes the other — we are missing an important dimension of the human story. We cannot ignore war and its impact on the development of human society if we hope to understand our world and how we reached this point in history.”

MacMillan is one of the most respected and widely read historians in the world. The Canadian-born MacMillan is the great granddaughter of British Prime Minister David Lloyd George.  A former provost of Trinity College at the University of Toronto and a former warden of St. Antony’s College at Oxford University, MacMillan is a respected scholar of international relations and history.

She notes that during her research and writing over the years, she has often been struck by the pervasiveness of war and has reflected on its alluring and terrifying qualities. In 2018, she accepted an invitation by the BBC to deliver the prestigious Reith lecture series and decided to analyze war as a “long-standing and integral part of the human experience.” These lectures were organized under the theme “The Mark of Cain” and inspired her new book, “War: How Conflict Shaped Us.”

The book — which was named one of the 10 best books of 2020 by The New York Times — is wide-ranging, readable, provocative and challenging. It is not obvious how to best examine a topic as all-encompassing as war. MacMillan tackles it shrewdly and thematically.

She begins by considering the relationship between human societies and war and concludes that “the evidence seems to be on the side of those who say that human beings, as far back as we can tell, have had a propensity to attack each other in organized ways — in other words, to make war.”

MacMillan observes that war is arguably the most organized of all human activities, and it has stimulated even further organization of society.

MacMillan ponders why groups have gone to war throughout history and identifies reasons such as religion, dynastic struggles, conquest, imperialism and revenge. “Yet certain motives appear again and again: greed, self-defense, and emotions and ideas,” she writes.

She also ponders why individuals have been willing to fight and identifies multiple motives. They have been conscripted or inspired to fight to protect loved ones and their nation. They have been motivated by a sense of honor, or a fear of rebuke or to win approval of those they respect. Some have gone to war to pillage, to gain glory, to advance a cause or to get ahead in the world. “For men war offers a chance to test themselves, against their peers, but also their elders.”

MacMillan examines how societies organize for war and how they fight. She posits that culture, technology and war are so interdependent that it is difficult to say which drives which. “It is another uncomfortable truth about war that it brings both destruction and creation,” she writes.

MacMillan considers how war affects civilians and observes that a deeply troubling feature of modern warfare is that non-combatants are often the targets of attacking armies. In World War II, for example, she reports that between 50 million and 80 million civilians perished.

Even as war persists, so have efforts to develop rules to limit and control it. An elaborate regime has been crafted to guide the initiation of, and justification for, war and to regulate its conduct. These rules have had a modest record of success.

MacMillan is intrigued by the many paradoxes of war. “We fear war but we are also fascinated by it,” she writes. “We may feel horror at the cruelty of war and its waste, but we can also admire the courage of the soldier and feel the dangerous power of war’s glamour. Some of us even admire it as one of the noblest of human activities. War gives its participants license to kill fellow human beings, yet it also requires great altruism. After all, what can be more selfless than being willing to give up your life for another?”

“War” is a wide-ranging and stimulating book that raises fundamental and profound questions. Is man genetically programmed to fight? Are war and humanity inextricably interwoven? Do changes in society bring new types of war or does war force change in society? Should we acknowledge that war and society are partners, locked into a dangerous but also productive relationship? Can war, with all of its potential for destruction, also bring benefits and improve societies?

War is repellant to most of us and we try to avoid thinking much about it. But MacMillan warns us that avoidance is not the answer. She urges us to confront basic questions about war.

“With new and terrifying weapons, the growing importance of artificial intelligence, automated killing machines and cyberwar, we face the prospect of the end of humanity itself. It is not the time to avert our eyes from something we may find abhorrent. We must, more than ever, think about war,” she writes.

“War: How Conflict Shaped Us” is an excellent way to begin grappling with the existential and essential questions about war.

John T. Shaw has been the director of the Paul Simon Public Policy Institute since January 2018. Prior to that, he worked for 25 years as a congressional reporter and diplomatic correspondent in Washington, D.C. He is the author of five books, including “Rising Star, Setting Sun: Dwight D. Eisenhower,” “John F. Kennedy, and the Presidential Transition That Changed America” and “JFK in the Senate: Pathway to the Presidency.”