Human rights activists are calling it the bloodiest 48 hours of the Syrian conflict to date. Over the course of Thursday and Friday, they say, more than 700 people were killed in clashes between the militant group known as the Islamic State of Iraq and Greater Syria (ISIS) and government forces. While the scale of such a massacre is staggering, the downing of a Malaysian passenger plane over Ukraine and Israel’s escalating attacks on Gaza dominated international headlines last week, leaving Syria’s grief relegated to the back-burner.

The head of the Syrian Observatory for Human Rights, a United Kingdom-based group that has monitors the conflict, told reporters that this was the first time the death toll has topped 700 in the span of two days since the civil war broke out in 2011. The fighting last week came as ISIS — also known as the Islamic State of Iraq and the Levant (ISIL) — struggled to wrest control of the Shaar oil field, east of the Syrian city of Homs, from forces in support of President Bashar al-Assad. ISIS announced the creation of a new Islamic caliphate late last month and demanded obedience from all other Islamic militant groups.

The terrorist group has made significant territorial gains over the past few months, capturing major cities in northern Iraq such as Mosul and continuing to expand its control over Syria. Its advances into Syria have been facilitated in large part by the weapons it captured from the retreating forces of Iraqi Prime Minister Nouri Al-Maliki. ISIS does not limit its attacks in Syria to government forces alone, but rather seeks to rid eastern Syria of the moderate rebel factions who also oppose Assad, as well as ethnic Kurds. Last Monday, ISIS expelled both more moderate rebels and other jihadi groups from Deir al-Zor city, the largest in eastern Syria. As ISIS tightens its grip over the oil-rich region bordering Iraq, Assad’s forces have responded by mounting several retaliatory airstrikes.

Direct confrontations between Assad’s army and ISIS have actually been quite rare. Earlier this month, government soldiers were allowed to mount a siege on the rebel stronghold of Aleppo and take control of the industrial area of the city, unopposed by ISIS. In contrast, Syria’s moderate U.S.-backed opposition has been increasingly plagued by lack of organization and a costly two-font war against ISIS in the east and Assad’s regime in the north. And the moderates have suffered just as much from infighting as from their soldiersdefecting to the better armed and better organized ranks of ISIS, which often provide higher pay and more protection.

Leaders of the Free Syrian Army, the main secular group fighting to retain control of Aleppo, have been pleading for months for more military aid from the West. But a serious lack of cohesion between even the various moderate factions fighting Assad suggests their recent losses may be tied to deeper problems that weapons shipments alone can’t fix. Now, the moderate opposition is nearing collapse. Damascus announced Monday that it is sure of victory due to its Russian backers. However, last week’s massacre suggests that the absence of hostilities between Assad’s army and ISIS won’t last for long.

Inside ISIS-controlled territory in Iraq and Syria, the group is attempting to fulfill all the functions of a state. Meanwhile, they’re also trying to enforce a strict interpretation of Islamic law and carrying out human rights abuses that threaten to alienate many accustomed to years of relatively secular rule. Considerable funding from wealthy Gulf states has allowed ISIS to repave roads, set up courts, and institute an export system for smuggled crude oil. While they enforce Islamic Shariah law in a patchwork fashion, highly dependent on the directives of local administrators, ISIS has enacted harsh persecutionagainst Christians and other religious minorities and stoned two women to death for adultery over the weekend in Syria, attracting international condemnation.

In its attempts to dominate Syria and Iraq, ISIS is bolstered by as many as 10,000 foreign fighters who have flocked to Syria and Iraq to take part in the war to establish an Islamic state. New fighting on Monday between ISIS and Assad’s forces near Damascus goes to show that the civil war could be entering a new, intensified stage of violence, and that the conflict is certainly nowhere near winding down.

BY WILL FREEMAN

Think progress