ISTANBUL/BEIRUT - The Hazzm movement was once central to a covert CIA operation to arm Syrian rebels, but the group's collapse last week underlines the failure of efforts to unify Arab and Western support for mainstream insurgents fighting the Syrian military.
A blow to US moves to aid rebels, the dissolution of Hazzm also highlights the risks that a new Department of Defence programme could face in training and equipping fighters in Jordan, Turkey and Qatar.
US officials plan to train thousands of Syrian rebels over three years. The programme is expected to begin this month in Jordan and focuses on battling the hardline Islamic State group rather than President Bashar al-Assad.
Hazzm's collapse has shown how such efforts will prove difficult in a country where insurgents often battle each other and arms have fallen into the hands of hardline groups.
An onslaught by al Qaeda's Syria wing, the Nusra Front, last week forced Hazzm into dissolution, its members swallowed by Jabhat al-Shamiyya, a mainly Islamist alliance. It was the second time in four months that Nusra had crushed a Western-backed rebel group.
Nusra is now considering cutting its ties with al Qaeda in a rebranding exercise backed by Qatar and some other Gulf states that will bring in more funds, sources say.
On Tuesday, Nusra followers published photographs on Twitter of what they said were US weapons, including anti-tank missiles, seized in battles with opposition brigades.
Reuters could not authenticate the photographs but the head of the Syrian Observatory for Human Rights, Rami Abdulrahman, said many arms had been seized, including 60 to 90 TOW anti-tank missiles.
Hazzm members did not respond to requests for comment or were not reachable. The group once claimed to be the main recipient of the secret US-led operation supporting rebels in the north. It numbered 1,200-1,500 last year, Abdulrahman said.
It was set up in January 2014 and came under a body known as MOM, which was used to funnel resources to rebels in an attempt to coordinate funding. Money has poured into northern Syria from Gulf Arab states including Saudi Arabia and Qatar, much of it going to Islamist fighters, including hardliners.
"The United States was never particularly serious in its support for the MOM, and coordination among the United States and other state backers broke down," said Noah Bonsey, a senior Syria analyst at the International Crisis Group.
"The defeat of Hazzm is the latest indication of the MOM's failure in the north," he said.
State Department spokeswoman Marie Harf said Hazzm had received non-lethal US assistance. Washington has never acknowledged the CIA programme.
The group's demise "will have an impact on the moderate opposition's capabilities in the north," Harf said.
The group had shrunk to about 400 fighters last month after killings, desertions and arrests, the Observatory's Abdulrahman said. "They are now finished, like sugar in tea."