The Syrian army has started erecting a 100-kilometer-long (62-mile) line of military positions east of Damascus in recent weeks, in an effort to protect the capital from possible advances by Islamic State forces.

The move comes after the repeated failures of President Bashar Assad’s forces against the rebels this spring, and constitutes an admission by the regime that there may be a huge battle for control of the capital within a short time.

Israel, however, doubts that establishing the line will be enough to block Islamic State (also known as ISIS or ISIL) in the future. It also believes the regime may end up having to relinquish Damascus in order to defend the Alawite enclave in the country’s northwest.

The line of outposts, which includes small military camps, embankments and access roads, is now being built some 80 kilometers east of Damascus International Airport, which is itself east of the capital. ISIS forces are concentrated mostly east of there (scoring a success last month with the capture of Palmyra in the Syrian Desert), although the organization has operated previously both in Damascus neighborhoods and the Yarmouk refugee camp on the city’s southwest outskirts.

It’s doubtful if this line of positions will be an effective response to the Sunni group’s modus operandi, which is based on the rapid movement of armed jeeps and the surprise appearance of underground cells deep in enemy territory.

It seems as if the building of the defense line reflects the pressure on the Assad camp given recent rebel achievements, with the regime losing its control of territories in Idlib Province in northern Syria, while it has been unable to retain almost any control along its border with Israel on the Golan Heights.

Last week, the regime suffered another military failure when the Southern Front – which incorporates several Sunni rebel groups, including the Nusra Front (though not ISIS) – seized the headquarters of the 52nd Brigade. This is a huge military base in the south of the country, north of the town of Daraa. The location of the base puts the regime’s control over the main road leading from Daraa to Damascus at risk.

The Syrian army has also withdrawn a substantial number of its troops from the Jabal al-Druze mountain range and moved them closer to Damascus.

Although it seems these various rebel groups, who aren’t really coordinating with each other, will continue to advance, it isn’t clear what their priorities will be over coming months. The momentum of Jaish al-Fatah (“The Army of Conquest”), a front made up of eight Sunni rebel groups in the north, is liable to lead to continued attacks in the northwest, in the direction of the Alawite region, as well as progress toward Damascus.

On the Syrian-Lebanese border, particularly in the Qalamoun mountains, battles continue between Hezbollah and the Lebanese army on one side, and radical Sunni groups on the other. In this region, neither side has been able to make substantial progress.

Iran and Hezbollah continue to support Assad, but Tehran has refused the Syrian president’s request to send Iranian troops to help in the fighting. The Iranians seemingly want to avoid drawing international criticism just when they’re reaching a critical stage in their nuclear talks with the six powers (the deadline is on June 30).

Qassem Suleimani, commander of the Quds force of the Iranian Revolutionary Guards Corps, is continuing to direct the moves of Syrian forces and Hezbollah fighters. In addition, thousands of Iranian experts and intelligence officers are in Syria assisting the regime. But Iran is still wary of sending in operational forces to directly confront the rebels in battle.