Lee Smith explains in TNR: Damascus’s Deadly Bargain:
To better understand Syria’s motivations, I visited Abdel Halim Khaddam, Syria’s former vice president, in Brussels, where he was leading a meeting of the National Salvation Front (NSF), a Syrian opposition group. Having served under both Hafez al-Assad and his son Bashar, Khaddam is well-acquainted with the strategic and political exigencies driving the regime’s support for terror. “Fighting the Americans in Iraq is very dangerous,” he tells me. “But it also makes Bashar popular. Under the banner of resistance, anything is popular.”
…when Hezbollah went to war against Israel in the summer of 2006, it hurt not only Israel but the majority of Lebanese, who were not standing with Hezbollah. But Syria’s logistical, financial, and political support for the Islamic resistance burnished Assad’s credentials at home, while also earning him respect across the region. If other Arab rulers, like Egyptian president Hosni Mubarak and Saudi king Abdullah Al-Saud, were, in Assad’s words, “half-men,” the Syrian had shown himself to be a citadel of anti-Zionist, anti-Western resistance, the most popular Arab leader after Hezbollah’s Hassan Nasrallah.
Support for terror is also a significant element in Syria’s attempt to exert power over its neighbors. In addition to hosting groups that target Israel, like Hamas and Hezbollah, Syria has long maintained a broad portfolio of regional terror outfits, from secular organizations like Abdullah Ocalan of the Kurdish Worker’s Party (PKK) and Palestinian rivals to Yasser Arafat, to Salafi groups like Shaker al-‘Absi’s Fatah splinter organization, Fatah al-Islam. And as the recent US attack on Bou Kamal illustrated, Damascus hosts significant Iraqi assets, such as Al-Qaeda in Iraq…
..Nahas’s father-in-law, Ali Sadr al-Din al-Bayanouni–the leader of the Syrian Muslim Brotherhood in exile, who spent two decades living in Jordan–is himself an illustration of this strategy. Amman’s relationship with the Syrian Muslim Brotherhood is part of a long-standing rivalry, in which the Jordanians back Syrian Islamists like al-Bayanouni as a threat to the Damascus government, and Syria, in turn, supports elements of Jordan’s Islamist opposition, like the Islamic Action Front. While this game of chicken seems to risk Islamist blowback, it is a key strategy in Arab balance-of-power politics.
The Syrians have similarly managed their relationship with Saudi Arabia, which has been at an all-time low since the 2005 murder of former Lebanese prime minister and Saudi ally Rafiq al-Hariri, which the Saudis blamed on Damascus. In December 2005, Khaddam made a big splash in the first part of a televised interview on the Saudi-owned Al-Arabiya satellite network charging Bashar with the assassination, but then the Saudi royal family pulled the plug on the second part of the interview. The public rationale in Arab circles is that the Saudi kingdom is not in the habit of bringing down fellow Arab regimes. More likely, however, is that Damascus has an important card to play against the Saudis, who fear that Syria is holding several hundred Saudi fighters in prison; Damascus could embarrass the Saudis by publically announcing the existence of these extremists–or even worse, allow those jihadis to return home to fight the House of Saud.
This kind of leverage is not the only reason Syria keeps its jails stocked with foreign terrorists. According to Ghassan al-Mufleh, an NSF member who spent 12 years in Syrian jails for his Communist activities, this is also one of their primary ways of collecting intelligence, as well as tapping foreign agents to do their bidding abroad and subvert Arab rivals. Since Syria does not require visas from Arabs to enter the country, many terrorists use it as a transit point to places like Iraq, “so if they return from jihad alive and want to head home–Egypt, Saudi Arabia, Morocco–they just say that they were working in Syria,” Mufleh tells me. But this free flow also allows the Syrians to detain valuable operatives and “give them a choice–either they can agree to work for the Syrian services or they will be turned into their own home intelligence agency,” he says. “It is an easy choice.”