On Monday, a suicide bomber from the Islamic State of Iraq and the Levant (ISIS) drove a car laden with 1.5 tons of explosives into a Syrian military checkpoint at the busy eastern entrance to the government-controlled city of Hama. More than 30 people died, including civilians. The audacity of the attack signaled a shift in al-Qaida's Syrian military tactics, and its rising confidence in an increasingly fragmented rebel state.
"We've seen the use of suicide bombs and big bomb attacks ever since Jabhat al-Nusra first emerged in January 2012, but we have certainly seen a spike in the number and scale of such attacks in the last two to three weeks," says Charles Lister, analyst and terrorism expert at IHS Janes in London.
"It's the result of increased confidence. They've clearly got militants willing to carry out such attacks, and they've [now] also got the ability to fill vehicles with explosives and attack various government facilities."
The Syrian conflict is approaching its third year as a strategic stalemate, with months-long battles waged between rebels and government forces for terrain as small as one street or one complex. The battle for Aleppo's Minnagh air base dragged on for 10 months before ISIS arrived to help Free Syrian Army fighters, using suicide bombs as an effective method of leading the rebel takeover.
"They realize that suicide bombs can be very effective as a military tactic," says Aymenn al-Tamimi, an expert on Syrian jihadist groups at the Middle East Forum, a Washington-based think tank.
"It's clear at Minnagh that the use of these bombs ultimately helped bring about the downfall of the base," he said.
"As a military tactic it's very effective and can achieve [in a few hours] what could take months of [regular fighting]. There's one case where they recruited a Syrian in Aleppo to carry out a bombing against a high school graduation that was happening in a government-held area. It's a terrorism tactic to strike those who are seemingly in support of the regime."
The string of bombings is changing the long-held perception that ISIS does not get involved in front-line fighting, but rather keeps focus on consolidating its power in rebel-held areas, exploiting the power vacuum.
"It's part of a general military tactic now. There's a new front that opened up in Homs, a Jabhat al-Nusra and ISIS front against other rebel battalions and the regime," says al-Tamimi. "They're building up their [Islamist] state in their strongholds, but it's clear, with their [recruited] foreign fighters in particular, that they also wants to lead military offenses."
A major reason is that it's a way to attain new, powerful weapons. With the weapons cache taken from Minnagh, he says, "look how easily they crushed Northern Storm in Azaz."
But for all the spoils, ISIS is treading a fine line with its new tactic. On the ground, civilian support is shaky as the group displays what many see as harsh attacks against those who do not follow their ideology. Syrian activists said this week that the group had executed a well-known activist in Raqqa and given another, in Aleppo, 50 bloody lashings.
The regular killing of civilians through suicide bomb attacks could alienate potential followers.
"We've seen attacks in the last two weeks that have had high numbers of civilian casualties, even if they're [carried out] in government areas. That doesn't go down well on either side, pro-regime or pro-government, of the civilian population," Lister says. "The military impact can be significant, if they are targeting things like military bases, or if they hit in the middle of city at security checkpoints.
"Those attacks do risk damaging the levels of civilian acquiescence [and support]. With Nusra, we've seen an increasing indication the last few months that's it's beginning to be accepted on the ground as the mainstream Islamist actor. But if they continue to carry out these large suicide bombings, it's very feasible that civilians' willingness to follow it will decrease."
As ISIS recruits new members in Syria and imports others from abroad, Tamimi says the number of bombings will likely continue to rise. "We'll see more in the Damascus area, because they're always trying to advertise that they have a presence there, especially in Ghouta [site of the Aug. 21 chemical weapons attacks allegedly carried out by Assad]. I don't think they'll use them against other rebels. We would [only] see that in a post-Assad scenario where there's more intra-rebel infighting.
"It's an outgrowth of ISIS and Jabhat al Nusra ideology: wherever they are, suicide bombs will show up."