THE FIFTEEN BRANCHES of Syria's intelligence apparatus, the mukhabarat, count some 50,000 to 70,000 full-time officers, along with hundreds of thousands of part-time personnel and informers. By 2011 it was estimated there was one intelligence officer for every 240 or so Syrians. A third of the country’s military budget has historically gone to the security services, including the Palestine Branch of Military Intelligence, which does not gather intelligence against Israel (the regime’s nominal enemy), but rather monitors Syria’s 500,000-strong Palestinian population (along with many Syrians) and runs a notorious detention and torture center in Damascus. “The garbage collectors are intelligence agents,” a protester told the Associated Press after 120 people were killed in two days of protests in April 2011. “Sometimes we think even our wives are working with the intelligence. All the phones are monitored. We live in hell.”

This was the reality in Syria long before the start of the popular uprising in March 2011. Hafez al-Assad, the Baath Party general who seized power in 1970 from a group of other Baath Party generals, ruled for 30 years through coercion and brutal suppression, and filled the high ranks of the state’s many military and intelligence agencies with fellow Alawites. But he also maintained power through a “Faustian bargain,” as David Lesch writes in Syria: The Fall of the House of Assad, in which Syrians traded — or were forced to accept — a loss of political, economic, and social rights for a level of stability. For a country that by 1970 had seen 21 coups and countercoups — many of them bloody and led by rival military men — since its independence from French colonial rule in 1946, this was the Assad deal: one family, father and son, ruling Syria ever since.

But now Lesch, who in the early 2000s used unique access to the new president to craft a softly lit, optimistic profile, The New Lion of Damascus: Bashar al-Assad and Modern Syria (Assad is one of Arabic’s many words for “lion”), believes that era is finished. “Whether or not he remains in power, Bashar Al-Assad, in my mind, has already fallen,” he writes at the outset of his new book, a kind of mea culpa by an academic who believes he “got to know Assad probably better than anyone in the West.” The Fall of the House of Assad is a reappraisal that struggles to match his earlier auspicious impressions with the brutality of a regime that seems bent on destroying Syria to keep it a family domain.

Months after the uprising began, Lesch still had close enough contact with the regime to write emails to Assad’s personal advisor, Bouthaina Shaaban, including one in which he advised “Bashar” to “consider measures of true political reform rather than pieces of co-optation masquerading as reform.” Lesch doesn’t know if Shaaban forwarded these messages to Assad, or if she herself even read them. “But I have been told by Syrian officials that my comments and suggestions are taken seriously,” he writes. “This is perhaps why the Syrian mukhabarat did not particularly like me: it considered my access to be dangerous.”

In a 2007 trip to Syria to meet and interview Assad, Lesch was detained at Damascus’s airport, where security agents interrogated him for three hours. A colonel twirling a pistol was only convin...