Foreign Militias in Syria

Syria's civil war has definitely drawn in, not so much neighboring governments, but neighboring populations.  Lebanon was affected by tactical operations across the porous border even before Hizbullah went all in on behalf of the Assad regime, perhaps leading to long-term changes in the organization itself:

Hezbollah succeeded on the Syrian battlefield in chasing rebels from the border towns where many of the attacks originated. The bombings have since stopped, leaving Lebanon’s Shiites grateful for Hezbollah’s intervention and luring a new wave of aspiring young fighters to the group’s training camps...

(F)or Hezbollah more than a year of combat has produced a new sense of purpose that extends beyond battling Israel to supporting its allies and Shiite brethren across the Middle East. And although its victories have come at great cost in lives and resources, it has also gained the rare opportunity to display its military mettle and earn fresh battlefield experience...

The group’s leaders dismiss the idea that they have strayed from their mission, characterizing the anti-Assad uprising as an international plot to undermine Israel’s enemies. They have also portrayed all the rebels fighting Mr. Assad as “takfiris”... and said that they pose a threat to the whole region, not just to Shiites.

The "takfiri" label is an Islamic derogatory term for those such as Wahhabis, al-Qaeda types, and many salafis who insist they are the only true Muslims, and hence that violence against other "false" Muslims, especially Shi'ites, is justified.  Assad, of course, took steps to make sure salafi militants were among his armed opposition and has portrayed the entire revolt against him as their doing.  Although I suspect Hizbullah's calculations in supporting Assad were based on his role as the group's major arms and funding conduit, the sectarian overtones which have come to dominate the Syrian war ensure the intervention will also be seen regionally in that light.

The same thing is happening in Iraq with an offshoot of Muqtada Sadr's movement called the Asa'ib Ahl al-Haq:

AAH, led by the increasingly powerful Shi’a political figure Qais Khazali, is a breakaway faction of the Shi’a Sadrist Movement and has formed its own political bloc, al-Sadiqun (The Honest Ones), which ran in alliance with Iraqi Prime Minister Nuri al-Maliki’s Dawlat al-Qanoon (State of Law) coalition in the April 30 parliamentary elections. The group’s militant wing is reported to be extensively trained, funded and supervised by the Iranian Republican Guard Corps (IRGC). Enjoying the personal patronage of IRGC commander Qassam Solaimani, AAH emerged as one of the most effective militant groups fighting against Coalition forces in Iraq and is considered one of the most important foreign Shi’a jihadist organizations fighting for the Assad government against the armed opposition in the Syrian civil war. Ten of the AAH members killed at the April 26 election rally were veterans of the group’s war effort in Syria. AAH officials publicly acknowledge their role in the Syrian fighting, even if only in a limited and altruistic capacity...

Asa’ib Ahl al-Haq has already stated that its official position is to defend the holy sites of Islam, which is the sacred duty of every Muslim, Sunni and Shi’a. Attacks on the holy shrines could trigger sectarian strife, which would bring about reprisals, as happened in Iraq with the destruction of the Askari Mosque, which led to sectarian strife. Therefore we are trying to spare the region this conflict by defending the [Damascus] Shrine of Sayida Zaynab and thus avoid the need for targeted reprisals.

It seems to me that there are more foreign fighters in Syria than there ever were in Iraq, largely because already organized militias have deliberately intervened on both sides.  One side effect of this, though, is likely to be a radicalization of some of those fighters in sectarian terms; when they return to Iraq and Lebanon, they might be especially primed to fight local Muslims of the other sect.