The main jihadist force, the Islamic State of Iraq and the Levant, now controls large swathes of Iraq's Sunni-dominated Anbar province, which borders Syria, and much of northeastern Syria.
There it's been escalating its operations to lay claim to as much of the region as it can before the Geneva 2 talks on the Syrian conflict, which could convene early in 2014.
ISIL now has its eyes on the key northern city of Aleppo, once Syria's commercial capital, and the surrounding countryside as it expands to consolidate control over the northeast and the important border with Turkey.
ISIL's dominance of the Islamic forces fighting Syrian President Bashar Assad's regime grows daily, and its eclipse of the more secular, nationalist rebel forces of the Western-backed Free Syrian Army becomes more complete.
ISIL's campaign got a major boost in July when al-Qaida in Iraq, led by the ambitious and aggressive Abu Bakr al-Baghdadi, attacked the notorious Abu Ghraib prison west of Baghdad and freed some 500 inmates, including dozens of senior jihadists.
Indeed, the breakout may have been planned for that purpose.
These seasoned veterans of al-Qaida's decade-long war in Iraq galvanized the jihadist campaign in Iraq and in neighboring Syria. Since that mass breakout, in which suicide bombers blasted holes in the walls for the prisoners, ISIL has ruled the roost.
In western Iraq, the jihadists, invigorated by their newfound strength in Syria, now have de facto control over whole towns.
The western desert in Anbar, a vast region along the leaky border with Syria, is now known as the "Jazeera Emirate."
The jihadists call the oil-rich Kirkuk region in northern Iraq the "Daash Emirate" because they have systematically killed or cowed the Baghdad government's forces there, and in neighboring Diyala and Salahuddin provinces, in recent months.
These areas are seen as the embryo of a broad jihadist enclave in a region where civilization began, bordering the oil-rich Persian Gulf, Iran and the Hashemite kingdom of Jordan, highly vulnerable and adjoining the West Bank where the Israelis are alarmed by a growing al-Qaida presence on their doorstep.
"Al-Qaida controls 40 percent of the desert area of Anbar province," says Sabah Karhout, chairman of Anbar's provincial council.
"It's expected that Anbar will serve as fertile ground for a real war in the next few months," Iraqi commentator Mushreq Abbas warned.
Veteran Middle East analyst Patrick Cockburn said ISIL's gains in Syria were dangerous enough "to frighten the U.S. and its allies into doubt how far they want to see President Bashar Assad replaced by Sunni fanatics."
The FSA leadership has reportedly dropped its demand Assad must step down before any negotiations can occur because it's more worried about the jihadists than it is about accommodating Assad.
The fear of a jihadist-led regime in Damascus, which under the Assads was secular and nationalist, has dramatically shifted perceptions of the Syrian conflict amid the growing polarization of mainstream Sunnis and breakaway Shiites taking place across the Muslim world.
"Important developments such as the weakening government grip in Anbar, centered on the towns and cities of the Euphrates, have not been properly reported," Cockburn said.
"Al-Qaida's once again making ground attacks on cities like Fallujah, from which it was driven by U.S. Marines in 2004.
"The same is true of the city of Mosul in northern Iraq, where ISIL is reported to levy protection money on everybody from the local greengrocer to satellite phone and construction companies -- bringing in a monthly revenue of $8 million."
This is happening, he explains, "because al-Qaida reinvigorated itself by its gains in Syria, and the Sunni community in Iraq -- heavily defeated after the fall of Saddam Hussein in 2003 -- could see the regional balance of power changing in their favor."
Iraqi Foreign Minister Hoshyar Zebari warned last week the "toxic" spread of jihadism in Syria is such that "the day will come, God forbid, when they will have another Islamic emirate."