According to the study released this week by the Meir Amit Intelligence and Information Center in Tel Aviv, there are currently 6,000 to 7,000 Sunni foreign fighters in Syria battling forces loyal to President Bashar al-Assad. The number of Shiite foreigners fighting on Assad's behalf is estimated at 7,000 to 8,000.
Syria has emerged as a powerful magnet for jihadist volunteers, who because of their religious fervor and outside financing play oversize roles in the fighting for and against the Assad regime, in what looks some days like a Sunni-Shiite proxy war.
Western and regional intelligence agencies worry especially about what these young men will do when they return to their home countries.
The majority of the Sunni fighters -- about 4,500 -- are thought to come from the Middle East and North Africa, especially Libya, Tunisia and Saudi Arabia. Some of the most experienced fighters come from Iraq, where they cut their teeth waging guerrilla war and terrorist campaigns during and after the U.S.-led occupation.
More than 1,000 are from Western Europe, mostly Belgium, Britain, France, Holland and Germany, according to the report. Many are the sons of second- and sometimes third-generation Muslim immigrants, especially Europeans of Moroccan extraction. Several hundred are Chechens.
The researchers found evidence of only a few dozen recruits from the United States and Canada. Also, the war in Syria appears to have inspired participation by just a relative handful of Palestinians from the Gaza Strip and the Israeli-occupied West Bank.
Experts say that, far more than Afghanistan or Iraq in decades past, Syria's rebel movement is drawing thousands of young men to fight.
“Because it is cheap, and it is easy,” said Reuven Erlich, a retired colonel in Israel’s military intelligence directorate and now director of the center that produced the report. “You can make jihad for the price of plane ticket to Istanbul.”
From there it’s an overnight bus ride to the Syrian border, where recruiters are easily reached by calling cellphone numbers widely in circulation.
Erlich said he was surprised how rapidly the numbers of foreign fighters rose in the later half of 2013.
This phenomenon is worrying, he said, because the young Sunni fighters are typically not joining the more secular, more pro-West Free Syrian Army, which the Obama administration supports, sort of. Instead, they often seek out al-Qaeda-affiliated organizations, mostly Jabhat al-Nusra, also known as the al-Nusra Front, and the Islamic State of Iraq and Syria -- “which offer better food, better weapons and jihad ideology.”
“They learn to fight, they become radical, more committed to jihad, and then they return home,” Erlich said.
The researchers found that an additional 7,000 to 8,000 foreign Shiites fighting in Syria on behalf of the Assad government, including at any given time “several thousand” members of the Lebanon-based Shiite militant group Hezbollah.
The Israeli figures largely track other recent estimates made by groups such as the Washington Institute for Near East Policy and the International Center for the Study of Radicalization in Britain.
Erlich and his team drew other conclusions, as well: The majority of foreign fighters are young men (average age 23 to 26), often with decent educations but no military experience, and so begin their service in support roles, as go-fers and cooks. They train for 45 days and their stays in Syria are often brief. Many leave for home after three to five months.
“Many come during their school vacations,” Erlich said.
Some are propelled by religious fervor, while others are looking for adventure, seeing the Syrian rebels as romantic figures, according to accounts offered by the fighters on Web sites read by the Israelis.
But it is no spring break. The Israelis estimate that 500 to 700 foreign fighters have been killed in Syria. Also in 2013 there were at least 16 suicide bomb attacks carried out by foreign fighters from Jordan or Saudi Arabia.
“We were surprised with the speed and depth of the phenomenon in 2013 compared to 2012,” Erlich said. “And we haven’t even begun to see the end of this.”