The Syrian rebel group Harakat al-Hazm, one of the White House’s most trusted militias fighting President Bashar al-Assad, collapsed Sunday, with activists posting a statement online from frontline commanders saying they are disbanding their units and folding them into brigades aligned with a larger Islamist insurgent alliance distrusted by Washington.

The statement bore Hazm’s stamp and logo, and according to the Syrian Observatory for Human Rights, a pro-opposition monitoring group, the brigade’s fighting units are disbanding. Emails and phone calls to Hazm’s political leaders were not returned.

“Given what is happening on the Syrian front, offenses by the criminal regime with its cronies against Syria as a whole, and Aleppo specifically, and in an effort to stem the bloodshed of the fighters, the Hazm movement announces its dissolution,” the statement said.

Charles Lister, an analyst with U.S, think tank Brookings, described in a tweet the implosion of the group as “absolutely remarkable.”

The apparent implosion comes just weeks after the Obama administration halved its funding of the 4,000-strong secular brigade—one of several more moderate rebel militias that have seen their U.S. funding cut or scaled back since Christmas.

Hazm has suffered an increasing number of defections in recent weeks in the face of repeated attacks from al Qaeda affiliate Jabhat al-Nusra on its remaining redoubts in Aleppo and in the area west of the city.

This weekend the brigade suffered 300 casualties, say opposition officials, from fighting with the jihadists, and its leaders say that to avoid further bloodshed they have had no choice but to dissolve themselves and throw in their lot with the larger Shamiah Front, an alliance of mainly-Islamist militias in Aleppo. They say the morale of the militia—one of the few rebel brigades to have been trusted in the past by the U.S. with TOW anti-tank rockets—had plummeted as the American money spigot was slowly turned off.

A U.S. official said the secular militia had no alternative but to disband. He said it will now be crucial to see what individual Hazm fighters do, indicating that he hoped some would volunteer for the train-and-equip program..

A 50-man intelligence unit formed by Hazm to assist in on-the-ground damage assessment of U.S. airstrikes on ISIS and to provide information on al Nusra was disbanded because of the funding reductions, a senior opposition source told The Daily Beast.

The cuts in Hazm’s funding coincided with Obama administration aides claiming they were ramping up their efforts to launch a train-and-equip program—promised since September—for rebel militias, part of a U.S. effort to form a proxy force to battle the so-called Islamic State, commonly known as ISIS.

Hazm was frequently touted by Obama aides as one of the militias they could rely on—a brigade that could partner on train-and-equip.

But like other moderate militias, the program didn’t sit well with Hazm fighters, who were infuriated with Washington at what they saw as a downgrading of their efforts to topple President Assad.

Hazm’s problems with al Nusra, al Qaeda’s franchise in Syria, have multiplied since late October when their jihadist foes overran several of the militia’s key strongholds in Idlib, including Khan al-Subul, where it stored about 10 percent of its equipment. Hazm denied reports that al Nusra fighters managed to seize U.S.-supplied TOW anti-tank missiles, but conceded that al Nusra was able to secure 20 tanks, five of which were fully functional; six new armored personnel carriers recently supplied from overseas; and dozens of the group’s walkie-talkies, which Hazm leaders bought themselves from Best Buy during a visit to the U.S.

As al Nusra pressed attacks on Hazm in Idlib province and also on the moderate Islamist rebel alliance, the Syrian Revolutionaries Front, commanders from Hazm appealed privately to the Obama administration to help them. That help never came.

The brigade’s failure to hold the line against al Nusra—as well as the failure of other Western-backed armed groups to assist the beleaguered Hazm—was one of the reasons given to The Daily Beast by a State Department official for the cutbacks in funding for several rebel groups.

Another reason cited was the increasing tendency of the moderate and secular militias to coordinate with the Shamiah Front.

That alliance was formed on Christmas Day for the defense of besieged rebel-held areas in Aleppo, where Assad had launched a major offensive to encircle them. The front includes not only hardline Salafist factions from the groups known as the Islamic Front but more moderate brigades like the Muslim Brotherhood-linked Mujahideen Army and Harakat Nour al-Din al-Zenki, a militia that has also received TOW missiles from Washington in the past.

Aleppo-based rebels insist they have no choice but to work with the Front, which also coordinates operations against Syrian government forces inside Aleppo with al Nusra. “Without the front, Assad would overwhelm us,” says a secular rebel commander. He and other brigade commanders say the Obama administration’s train-and-equip plan has little to do with what is unfolding rapidly on the ground. Brigades are demoralized, disintegrating, and fighting among themselves.

The train-and-equip program has also earned sharp criticism from some U.S. lawmakers, who say it lacks clarity and has promoted profound suspicions among rebel groups that Washington is ready to cut some sort of deal with Assad while expecting Syrian rebels to sacrifice themselves to fight ISIS. Referring to the poorly planned and futile Confederate assault at Gettysburg, Sen. Lindsey Graham of South Carolina has likened the strategy to Pickett’s Charge.

In recent days Hazm’s fight against al Nusra appeared even more forlorn. On Wednesday the jihadist group, which in effect has carved out an emirate of its own in Idlib, declared an all-out war on Hazm, accusing it of fomenting the conflict by arresting and executing their fighters in the west of Aleppo. Hazm commanders say all they have been doing is defending themselves.

“Jabhat a-Nusra, from the date of this announcement’s publication, considers what was has been called ‘Harakat Hazm,’ in all its components, a direct target,” the al-Qaeda affiliate said in a statement Wednesday. Hazm responded on Thursday, saying al Nusra had been abducting and attacking their fighters.

On Saturday, al Nusa fighters drove the U.S.-backed rebels out of a strategic northern military base in a battle that left dozens dead, activists said. At least 29 Hazm fighters and a half-dozen Nusra jihadis were killed in fighting for control of Base 46, a former regime facility west of Aleppo and Hazm’s last major redoubt in the Aleppo countryside, according to the Syrian Observatory for Human Rights. Residents in a nearby rebel-held village of Atareb criticized the jihadists for the attack and appealed in a statement to al Nusra to fight the “infidel regime and its allies” instead.

While al Nusra has been fighting the moderate armed opposition to Assad, it has been left alone by rival ISIS, with clashes between the competing jihadists all but ceasing.