Islamist fighters from Syria, including elements from the Islamic State of Iraq and Syria (ISIS) and Jabhat al-Nusra, have now killed 10 Lebanese soldiers and captured more than a dozen others in an offensive on checkpoints controlled by the Lebanese army. The battle in the northern Lebanese town of Arsal is the latest round of spillover from Syria’s conflict into Lebanon.

Extremist fighters based in Syria are thought to have been behind numerous car bombs in Beirut, often targeting neighborhoods considered strongholds of Hezbollah, the Shiite militant group that has been fighting in Syria alongside Bashar al-Assad.

But as extremists drove through Arsal on Saturday, many wondered if Lebanon had reached a watershed moment.

General Jean Kahwaji, the head of the Lebanese Armed Forces (LAF), said the insurgents’ attack was well-prepared and coordinated, the New York Times reports. By Sunday jihadists had seized Arsal; the LAF had surrounded the town and shelled it, in a bid to retake control.

We asked Faysal Itani, a fellow at the Atlantic Council focusing on Hezbollah’s involvement in Syria and the crisis’s spillover into Lebanon, and Theodore Karasik, research director at Dubai-based thinktank INEGMA, to weigh in on how events could play out for the LAF, Hezbollah and the Syrian extremists fighting on Lebanese terrain.

Syria Deeply: Why did extremists stage this attack now?

Faysal Itani: Because the Lebanese armed forces and Hezbollah at the same time are carrying out an operation to clear eastern Lebanon, and the mountains between Syria and Lebanon, from Syrian militant groups. And they’re going after them quite aggressively. The LAF is going after them in Lebanon, and Hezbollah is going after them in Syria in the area along the border.

So one way to look at this in terms of timing is as a reaction or preemptive action against an operation that has been going on for a few weeks now. Obviously the LAF is one of the belligerents in this conflict, and so is Hezbollah. They intercept a lot of weapons and fighter flows into Lebanon, and go after them in Arsal, where they’ve established a presence. In some cases they hand them over to Syrian security forces. The LAF is the rear guard of this operation, and Hezbollah is the offensive side.

Ted Karasik: This is not the first time that northern Lebanon has been faced with this kind of threat from salafists from Syria. It is likely that there will be more pitched battles that will continue, but in terms of having big advances into Lebanon, I don’t think that will occur because the Sunnis of northern Lebanon and the extremist tendencies there do not favor at all those of al-Nusra and ISIS. But it will continue to be bloody.

It’s part of the natural progression of the expansion of the battle space. Nusra is conducting an expansion of the front, trying to punch a hole into northern Lebanon. But I think it’s going to be a long time until the Sunnis in that area acquiesce.

Syria Deeply: How will this play out?

Itani: These groups have been operating in Lebanon for a while now. They have carried out numerous attacks in southern Beirut. Their ability to carry out those attacks has been hurt now, because Hezbollah and the LAF have been going after them in Lebanon, in the areas where they have been making bombs and planning attacks.

I don’t think [the extremists] are going away, but the combined efforts of the LAF and Hezbollah – as long as the LAF remains a unified entity – means they can’t gain a really strong foothold in the Bekaa Valley. Where they might be able to present more of a challenge is in northern Lebanon, where there is some growing sympathy for these jihadist groups. Of course the north is the least developed, poorest part of the country, which helps their cause. But the LAF and Hezbollah are a capable force together, and Lebanese Sunnis don’t generally have extremist tendencies. So I don’t think this will be an area of great success for jihadist groups.

Karasik: Are we crossing the rubicon, will Hezbollah have to get involved? We’ll have to wait and see. The LAF should be able to take care of this problem itself; it has had a lot of experience with this kind of activity in terms of counterterrorism. They will have a better handle on the situation domestically, which may keep Hezbollah out at least in the short term.