AL-QARDAHA, Syria—On the fourth day of a rebel assault on President Bashar al-Assad ’s seat of power in Damascus, an explosion tore through offices of the National Security Bureau, killing the president’s brother-in-law and three other senior officials.
Rebel groups claimed credit for the audacious plot, and Syrian opposition groups declared it was the beginning of the end for the regime. In Washington, the Obama administration ordered a task force from the Pentagon, State and Treasury to draw up plans for a post-Assad Syria, said Robert Ford, the U.S. ambassador to Syria at the time.
The July 2012 bombing indeed marked a turning point in Syria’s conflict. But rather than the downfall of Mr. Assad, it ushered in a new, more deadly phase of Syria’s civil war that allowed him to cling to power. Any regime voices still open to accommodating the opposition went silent, and, within a year, pro-Assad forces deployed chemical weapons against rebels and civilians.
Now, new revelations point to a startling theory about the bombing that killed Assef Shawkat, an army general who was Mr. Assad’s brother-in-law and the deputy defense minister: It was an inside job.
Two dozen people, including past and current regime officials, opposition leaders, activists and rebels, and politicians in neighboring countries with ties to Mr. Assad told The Wall Street Journal the bombing grew out of a split between the Assad family and its hard-line allies on one side, and officials seeking negotiations with opposition groups on the other.
Acceptance of the theory by such a broad cross-section of Syrians highlights the ruthless reputation Mr. Assad has cemented since the conflict began more than three years ago. It also shows the dynamic of the president’s inner circle as it struggled to keep a grip on power.
Mr. Assad’s media office rejected requests for an interview with the president. Maj. Gen. Ali Mamlouk and Maj. Gen. Deeb Zeitoun, two of the regime’s top security officials, declined separate requests for comment.
Former Syrian army general Manaf Tlass believes the regime was connected with the bombing. Mr. Tlass defected two weeks before Mr. Shawkat was killed—after guards found six explosive devices planted outside Mr. Tlass’s office on a military base in Damascus. He accused the regime of wanting to kill him, too.
Mr. Tlass said he and Mr. Shawkat were among those calling for talks with both peaceful and armed regime opponents, a position contrary to Mr. Assad and his intelligence and security agency chiefs, who sought to crush the insurgency.
“Bashar never opted at any time for serious and credible reforms, but instead chose to destroy the country rather than lose power,” said Mr. Tlass, who is living in Paris. “He sold Syria to the Iranians.”
The attack opened the door for Iran, Mr. Assad’s principal regional ally, and Hezbollah, its proxy militia in Lebanon, to play a greater role in defending the regime, according to members of Syria’s security forces and pro-regime militias. Within weeks, foreign Shiite militiamen flocked to Syria. The fighters joined homegrown militias trained by Iran and Hezbollah to help prop up the overstretched Syrian army.
These fighters took the lead in the regime’s recapture of rebel territory, helping push the death toll from less than 20,000 at the time to more than 190,000 as of August, according to the United Nations. Millions more Syrians have fled their homes amid the destruction.
Iran’s embassy in Damascus and a spokesman for Hezbollah in Beirut refused interviews or comment.
Mr. Ford, who now works with the Middle East Institute, a nonpartisan think tank in Washington, said top members of the Syrian opposition told him rebels weren’t responsible for the bombing but believed the regime was. “I’ve never seen convincing evidence that it was an inside job,” he said, “but the allegations were widespread.”
A leading Syrian opposition activist, who had direct ties with rebel groups and was in Damascus the day of the bombing, said it would have been impossible for rebels at the time to carry out such an attack.
“If you asked me then, I would have lied to you and told you, ‘Our heroic rebels did it.’ But now I can tell you, ‘No, we were amateurs back then,’ ” said the activist, now based in Turkey. The bombing boosted opposition morale after government reports credited the rebels, he said. It also spurred more Alawites, members of Mr. Assad’s Shiite-linked minority sect who opposed the Sunni-led revolt, to rally around the regime.
Growing involvement by Shiite-dominated Iran and Hezbollah boosted support from Sunni Arab states and private donors to more militant rebel groups, including Islamic State, said Western officials and analysts.
Today, many Syrians—and the U.S. and its allies—face a choice between the Assad regime or the militants of Islamic State, which has turned large parts of Syria and neighboring Iraq into a magnet for foreign jihadists.
Long before Syria’s conflict began in the spring of 2011, Mr. Tlass and Mr. Assad—military academy classmates—were seen as a new breed of Syrian leaders: young, modern and open to reforms.
“Bashar started making reformist steps between 1998 and 2000, even before becoming president,” Mr. Tlass said. “I was close to him. People were hopeful and thought he was capable of changing things.”
Even the U.S. thought it could do business with Mr. Assad, reappointing an ambassador in Damascus in 2009.
The killing of two Syrian protesters by regime forces on March 18, 2011, in the city of Deraa, changed everything. It shattered a short period of peaceful marches by mostly Sunni crowds calling for Mr. Assad’s ouster.
Two days later, Mr. Tlass said, he got a call from Mr. Assad asking for advice. Mr. Tlass said he suggested Mr. Assad remove the governor of Deraa, release anyone detained in the demonstrations, arrest the local security chief and make amends for the killings with a visit to the city.
“I told him our society is tribal and will value your conciliatory gesture,” Mr. Tlass recalled. “He told me, ‘OK.’ ”
But as more protesters poured into the streets, more were killed. “It’s no secret that Syria is facing today a grand conspiracy whose threads extend from inside the homeland to far and near countries,” Mr. Assad said in a speech to parliament on March 30, 2011.
At the time, Mr. Tlass commanded a 3,500-strong unit within the Republican Guard that was charged with protecting the president and the capital. Mr. Tlass said about 300 of his men were sent to the city of Douma to help with crowd control as thousands of people took to the streets.
He said they were pushed aside by forces reporting to intelligence chief Hafez Makhlouf —a maternal cousin of Mr. Assad—who shot and killed about a dozen protesters in April 2011. Mr. Makhlouf couldn’t be reached for comment.
Mr. Tlass said some of his men were executed for refusing to shoot protesters. One of his best officers, he said, returned from Douma and pleaded to be relieved of the assignment.
“I told him, ‘Be patient, the president promised that things will be fixed within three weeks,’ ” Mr. Tlass said. “The next day, he committed suicide.”
Syria’s security and intelligence agencies believed they could rely on repressive measures that had worked for decades, according to former regime officials and Western diplomats.
Haytham Manaa, a Syrian opposition leader who has spent much of his life in exile in France, said the regime was surprised when people overcame fears and continued the street protests, which were inspired in part by the Arab Spring uprisings in Tunisia, Egypt and Libya.
Mr. Tlass said he retained his official position but was sidelined by the regime after he raised objections to shooting demonstrators and called for talks with community leaders involved in the protests. That view, he said, put him at odds with hard-liners close to Mr. Assad.
In May 2011, Mr. Tlass said, he had a last meeting with the president. “I told him, ‘I am your friend and I advised you not to choose the military solution,’ ” Mr. Tlass recalled. “ ‘Go for the political one, it’s more inclusive.’ He answered, ‘You are too soft.’ ”
Mr. Assad’s vice president at the time, Farouq al-Sharaa, one of the country’s most seasoned politicians, fell next. He was pushing for dialogue with opposition groups, his relatives said, and was put under house arrest shortly after he chaired a national dialogue conference in Damascus in early July.
Walid Jumblatt, a senior Lebanese political leader, said he last met with Mr. Assad in June 2011: “He told me at the end, ‘I don’t want people to love me, I want people to fear me.’ ”
Regime loyalists, meanwhile, took up the slogan: “Assad or nobody. Assad or we burn the country.”
In June 2011, some activists tried to keep their opposition movement peaceful amid the growing sectarian violence between the mostly Sunni rebels and regime forces, largely Alawite.
Mohammad-Mounir al-Faqir and fellow activists bought 5,000 ping pong balls that they covered with such slogans as, “Assad, we want freedom whether you like it or not,” Mr. Faqir said. They released the balls from a spot uphill from Mr. Assad’s residence and filmed guards scurrying to collect them.
By fall, rebels in Homs took control of neighborhoods by force. For the regime, the rebel advances threatened important roads connecting Damascus with Syria’s only seaports.
In December 2011, Mr. Shawkat, the brother-in-law later slain in the bombing, and two security chiefs visited Homs, Syria’s third-largest city, to meet with opposition activists, businessmen and religious and community leaders.
Mr. Shawkat and the others offered a cease-fire plan that would have committed the regime to end opposition arrests and the shelling of neighborhoods in return for a pledge by rebels to halt attacks on regime checkpoints, said people who were there.
One opposition activist said Mr. Shawkat seemed to be the regime representative most interested in the discussion. One of the businessmen there agreed.
“I told them, ‘You are turning people into your enemies, what’s your interest in that?’ ” the businessman said. “I was interrupted by an angry official but Assef [Shawkat] snapped at him and told him, ‘Calm down. Let him finish.’ ”
No deal was reached. Conciliatory gestures approved by Mr. Shawkat, such as allowing ambulances to pick up the dead and wounded, were blocked by regime hard-liners, according to activists and community leaders.
Mr. Tlass, the defected general, said Mr. Shawkat’s power diminished shortly after his return from Homs, as security and intelligence chiefs asserted greater control. “He insisted on retaining his functions and powers,” Mr. Tlass said, “and here the real clash began.”
Mr. Tlass and several people with knowledge of the matter said Mr. Shawkat posed a threat to Mr. Assad’s rule. Mr. Shawkat, who was married to Mr. Assad’s sister, had previously headed Military Intelligence—one of Syria’s most feared institutions—and commanded a loyal group of officers.
Mr. Shawkat moved within the circles of power that surround Mr. Assad. The first circles include Mr. Assad’s wife and mother, his army commander brother, Maher, and maternal cousins, the Makhloufs, Mr. Tlass said. The next circle includes the chiefs of security and intelligence services.
“In my opinion, they got rid of him. They were scared of him,” Mr. Jumblatt, the Lebanese politician, said of Mr. Shawkat. Others, including Mr. Tlass and people who know members of the Assad family, said Mr. Shawkat was seen as a potential threat to Mr. Assad.
Two months before the July 18, 2012, bombing, Mr. Tlass said, there was an unsuccessful plot to kill Mr. Shawkat with a poisoned takeout lunch of kebabs and hummus in Damascus.
The bombing marked a shift by Hezbollah and Iran—when saving the Assad regime became their top priority, according to Iraqi and Lebanese officials close to both sides.
On the day Mr. Shawkat was killed, Maj. Gen. Qassim Suleimani, commander of Iran’s elite Qods Force, was in Damascus, Mr. Tlass said. The Qods Force is a unit of Iran’s Revolutionary Guards responsible for operations abroad, particularly in Lebanon, Iraq and Syria.
Also that day, Hassan Nasrallah, commander of Iran’s main regional proxy force Hezbollah, spoke to supporters in a Beirut suburb to mark the anniversary of the 2006 war with Israel.
Mr. Nasrallah said Mr. Assad and his regime were indispensable for the survival of Hezbollah and other Iran-backed movements, including Hamas. Mr. Nasrallah said rockets fired at Israel in the war were Syrian.
A Syrian militia leader said in an interview last year that Syria’s intelligence services worked with Hezbollah and Iran’s Qods Force to raise fears that Sunni militants planned to attack holy Shiite shrines in Syria—an effort to attract more Shiites across the region to fight alongside Assad regime forces.
With the help of foreign fighters, the regime “succeeded in giving the impression of a strong and cohesive army,” said Ezzat al-Shabandar, an Iraqi Shiite politician with close ties to Iranian and Syrian regime officials.
The regime also began using social media to shift popular views toward the idea that opposition groups and rebels had joined savage Islamic extremists. Mr. Assad in speeches and interviews embraced the idea that he was an indispensable leader who must use violence to rescue Syria, a message that has echoed down the chain of command.
“I always tell Sunnis, ‘Your only protector is Bashar al-Assad because he’s restraining us and not letting us do more,’ ” said Col. Jamal Younes, an Alawite army officer.
Militancy on the opposition side also rose dramatically. By the spring of 2013, such extremist groups as Islamic State and the al Qaeda-linked Nusra Front were displacing both secular and homegrown Islamist rebel groups in Syria.
Islamic militants in March seized the predominantly Armenian-Christian resort town of Kasab, located in the mountains of Mr. Assad’s home province near the border with Turkey in western Syria.
Regime forces drove them out three months later, leaving homes and churches ransacked.
“We are victims of both sides and this is why I want to leave,” said Armen Georgekian, an Armenian Christian and the town’s only shopkeeper. He recalled visits by Mr. Assad before the conflict and said he and his group bought ice cream cones from his shop.
“He can survive,” Mr. Georgekian said, “but he can’t win.”
Down the coast is Mr. Assad’s hometown of al-Qardaha, which has been largely untouched by the war. A domed mausoleum stands on a hill where a dozen workers in late summer trimmed hedges and pulled weeds in its garden.
Inside, two guards in suits stood motionless next to a casket, covered in a green velvet cloth, that holds the remains of Hafez al-Assad, the Syrian president’s father and the founder of the Assad regime.
Around the casket in the black-marble hall are the tombs of two of Bashar al-Assad’s brothers, Majd and Bassel, who had been groomed by his father to take over power. Bassel al-Assad ’s death in a 1994 car accident opened the way for his younger brother, Bashar.
In Qardaha’s central market, shops were fully stocked and farmers from nearby villages hawked fruits, vegetables and freshly picked tobacco leaves.
A statue of Hafez al-Assad, surrounded by four lions symbolizing his four sons, stands in the main square.
Posters of Bashar al-Assad were plastered on shop windows. One showed him next to his father, who had a halo above his head. “Rest in peace in the heavens above, our master,” the caption said. “You should be proud of Bashar.”