Anthony Dworkin is a senior policy fellow at the European Council on Foreign Relations and was formerly executive director of the Crimes of War Project.

The war in Syria is the defining conflict of this decade. From its origins in peaceful demonstrations for political reform, the confrontation between the regime and its opponents evolved — through harsh repression and the militarization and radicalization of much of the opposition — into a regional and global proxy war. The Syrian regime has routinely committed war crimes and crimes against humanity, making a mockery of international hopes to protect civilians against atrocities. At the center of the regime’s savage deployment of force is Syria’s understated president, Bashar al-Assad, who has weathered international condemnation to emerge apparently secure in power.

Sam Dagher’s book “Assad or We Burn the Country: How One Family’s Lust for Power Destroyed Syria” gives a vivid and powerful account of the roots and course of the conflict, setting it in the context of Assad’s personal history and approach to power. Dagher scored a notable coup in writing the book by securing the cooperation of Manaf Tlass, a longtime family friend of Assad’s who was a general in the Syrian army before defecting to France in 2013. Tlass grew up alongside Assad in the inner circle of power in Syria. His father, Mustafa Tlass, was the inseparable colleague and partner of Assad’s father, Hafez al-Assad, who ruled Syria from 1970 to 2000, and he supervised Bashar’s accession to the presidency after his father’s death. Tlass’s testimony gives us a remarkable inside picture of the culture in which the younger Assad grew up and of his personal trajectory: the making of a war criminal, as Dagher’s account makes plain.

Bashar al-Assad was never intended to be president. His headstrong elder brother Bassel was being groomed for the position until his death in a car crash in 1994. Bashar was a quiet young man whose shy exterior concealed a calculating and determined ambition: He boasted to Tlass about his “detachment, rationality and coldness in tackling all matters, whether private or public.” Thrust into a position of leadership, Assad presented himself to the Syrian people as a modernizing and reformist president, but he wanted modernization only on his terms. He told Tlass that the only way to govern Syria was “with the shoe over people’s heads.”

The protests of 2011 apparently took Assad by surprise. He fancied himself as a very different kind of leader than the aging strongmen of Egypt, Tunisia or Libya who had been in power for decades. Dagher brings the protest movement to life by focusing on a few representative people who made the courageous decision to defy the regime. He shows how they were motivated by frustration at an intensely nepotistic economy (according to one estimate, Assad’s maternal cousin Rami Makhlouf controlled 65 percent of the Syrian economy) and long-standing hopes for political freedom that Assad had raised when he became president and then dashed. The book’s account of the evolution of the protests is detailed and valuable.

In his interviews with Dagher, Tlass presents himself as having argued that the regime should offer concessions to the protesters. However, he ultimately concludes that Assad had from the beginning sided with those pushing for a hard-line response. In pursuing this approach, the book suggests, Assad was following the playbook that his father had developed in ruthlessly crushing dissent, most notably in a brutal attack against an uprising in the city of Hama in 1982. The younger Assad’s distinctive contribution was to project a certain ambiguity about his position, maintaining a carefully cultivated facade of moderation and reasonableness while giving a green light for a violent crackdown.

Three aspects of the ensuing conflict emerge particularly strongly in Dagher’s account. First, he shows how sectarian tensions (above all between Sunni Muslims and Assad’s Alawite sect, an offshoot of Shiism) drove the escalation of mistrust and violence. Dagher, reporting for the Wall Street Journal, was the only Western journalist based in Damascus in the early years of the war. He offers a striking picture of the Shiite militias that sprang up to support the regime and oppose the largely Sunni uprising. Secondly, he gives an account of the way the regime tried to strengthen the more extremist elements among the opposition, deliberately releasing radicalized prisoners and secretly funneling weapons to the protesters to support the government’s narrative that its opponents were terrorists.

Finally, Dagher tells a more familiar but nevertheless important story of the way that regional and global powers came to shape the course of the conflict. The competing agendas of the Persian Gulf states and Turkey fueled divisions among the opposition, and support from Iran and Russia came to provide the backbone of Assad’s deployment of force.

The book is propelled by an underlying indignation at the regime’s brutality and the consequences it has had for Syria. At times Dagher writes that it was fear and lies that kept the regime in power, but elsewhere he acknowledges that a significant number of Syrians clung to Assad because they saw him as their protector against extremist violence. Dagher also berates the West for its failure to intervene more decisively; he suggests that the United States and its allies should have imposed a no-fly zone over parts of Syria to prevent the regime from bombing civilian areas. Yet he does not seriously consider the potential problems this might have caused, and the difficulty of striking a balance between the protection of civilians and escalating an armed conflict in which Western officials always believed a negotiated settlement was necessary.

Dagher criticizes Western analysts and humanitarian workers who called for accepting Assad’s likely survival in power and pursuing local cease-fire agreements, saying they helped Assad’s cause. But there was also a moral argument for this approach, based on the need to face reality and do whatever was possible to save civilian lives. In any case, questions about the policies of the United States and Europe lie outside the main story that Dagher tells so effectively. The debate over the lessons of the Syrian war will continue for years, and there are comparatively few politicians in the West who now argue that a more forceful response would have brought the violence to an end.

Assad or We Burn the Country

How One Family's Lust for Power Destroyed Syria

By Sam Dagher

Little, Brown. 564 pp. $29