It was the summer of 2012 and the young Jordanian was working long hours as a teacher at a vocational high school. He had just bought an apartment and a car. He was interested in getting married.
But just a few months later, he was making a long and dangerous five-day trek with other foreign fighters through the mountains that separate Lebanon from Syria. Angered by the plight of refugees and attacks on fellow Sunni Muslims by Syria's mainly Shiite and Alawite Muslim forces, the 28-year-old, who identified himself only as Abu Amr, had joined the rebel forces.
"Personally, I saw that as Muslims, our religion was under threat," he said via Skype, adding that his mother had encouraged him to fight. "My mother knew that if we died, it would be the best way to die ... protecting religion and Muslims."
When he arrived in Syria's Homs province, Abu Amr was part of a trickle of foreign fighters. Since then, as the conflict has grown bloodier and the forces more entrenched, a network of recruiters, coordinators and smugglers has evolved and brought in thousands more fighters from many countries.
U.S. intelligence officials say Syria has become the biggest magnet for Islamist fighters since the Afghanistan war with the Soviet Union in the 1980s.
"It's fair to say it's one of the top draws of recent history," said a senior U.S. intelligence official who spoke on condition of anonymity. "It's a very steady increase, and I expect that to continue as long as the fighting there continues."
A sophisticated recruiting campaign conducted openly on social media, including Twitter, Facebook and YouTube, seems to have played a large role in drawing the estimated thousands of foreign fighters who have come to Syria to fight for two Al Qaeda-linked rebel factions, Al Nusra Front and the Islamic State of Iraq and Syria, and other Sunni Islamist groups.
"In the age of social media, it's no longer that we have jihad videos put out on password-protected forums. It's very easy to put it out on open media so it opens it up to a wider audience," said Aymenn Jawad Tamimi, a Shillman-Ginsburg fellow at the Middle East Forum and a columnist at Jihadology.net. "If the social media output is anything to go by, it's bigger than anything we saw during the Iraq war."
Since the first days in Syria, when government forces cracked down on peaceful opponents, much of the conflict has been documented on social media.
One such video has been posted on the YouTube and Vimeo accounts of the Islamic State of Iraq and Syria. A man, his face covered in camouflage, stands in front of a playground and invites Sunni Muslims to join the fighting in Syria, warning that if Sunnis do not triumph here, they will face attacks elsewhere.
"These religion deniers will enter Mecca and Medina … if you don't come to jihad," the man said, suggesting that Alawites and Shiites would march on Islam's two holiest sites in Saudi Arabia.
That view of a stark battle between Muslim sects is shared by many streaming into Syria, including, on the other side, fighters from the militant Lebanese-based Shiite group Hezbollah, Shiite insurgents from Iraq and Revolutionary Guard members from Iran.
"Killing them is mandatory for us more than killing infidels," said Abu Amr, who described Shiites and Alawites as apostates who had left Islam. "We are ordered to create a caliphate to rule with God's law and protect Muslims' security and rights."
Two of Abu Amr's brothers and his brother-in-law are also fighting in Syria.
The foreign fighters come from "all walks of life, all different ethnicities" and from across the Middle East and North Africa, Europe, Asia and, in rare cases, the United States, American intelligence officials said. Most of the foreign fighters in Abu Amr's group are Lebanese, as is the leader of the group; others are from Algeria and Morocco. But a majority of the group is from Syria, as are most of the fighters in the war.
His group, whose name he didn't want published, is based near the Crac des Chevaliers, a medieval Crusader castle in western Homs province, where for months battles have raged and opposition-held towns have been under siege. It is unaffiliated with Al Qaeda-linked groups or the Western-backed Free Syrian Army, but it fights and coordinates alongside both.
Abu Amr, who was injured for a second time four months ago, now helps coordinate and share information with other rebel groups.
When he arrived last year, Abu Amr worked out his travel with Jordanian clerics who were in contact with clerics in Homs. He flew from Amman to Beirut and connected with smugglers who helped him trek into Syria carrying sparse belongings and $10,000 of his own money.
Now, "it is entirely different, in that it is much easier," he said. "There are coordinators who are responsible for this [smuggling people] in every area.
"Even many of the border guards look the other way in this matter because they have a vested interest in it," he said.