The research, conducted by the UK-based Conflict Armament Research (CAR) and funded by the European Union and the German government, showed 40 000 weapons recovered from ISIS since 2014.
A large amount of the retrieved armament were US arms either given or sold to jihadist rebel groups.
In one instance, an arsenal including anti-tank weapons switched hands from the US to so-called “Syrian rebels” to ISIS within just two months.
“Supplies of materiel into the Syrian conflict from foreign parties — notably the United States and Saudi Arabia — have indirectly allowed IS [ISIS] to obtain substantial quantities of anti-armor ammunition,” the CAR report states.
“These weapons include [anti-tank guided weapons] and several varieties of rocket with tandem warheads, which are designed to defeat modern reactive armor.”
The study did not speculate on whether the weapons had intentionally been given to the Islamic militant group. It is possible that ISIS might have stolen or captured US weapons, as in at least one instance, a US-backed militia is known to have had its weapons seized by Islamic militants.
Division 30, Syrian rebels armed and trained by the CIA, were ambushed by the al-Qaeda linked al-Nusra Front in August 2015, and the jihadists seized their materiel.
Some US-trained militants are however known to have defected to ISIS or al-Nusra, often takeing their weapons with them.
“These findings are a stark reminder of the contradictions inherent in supplying weapons into armed conflicts in which multiple competing and overlapping non-state armed groups operate,” the CAR report read. “Under such circumstances, it is difficult to exert effective control over which groups ultimately gain custody of the weapons.”
From 2013, the US supplied weapons and training to so-called anti-Assad rebels via the covert CIA program “Timber Sycamore” but US President Donald Trump announced the end of US support in July.
The US however continues to arm and support the Syrian Democratic Forces (SDF), a Kurdish group fighting ISIS. The SDF currently holds Raqqa, once the capital of ISIS in Syria, but notably the report found no evidence of SDF weapons falling into the hands of ISIS.
Other countries that have helped to arm, train, coordinate, or support insurgents in Syria, include France, the UK, Jordan, Saudi Arabia and Qatar. Turkey, too, deployed thousands of soldiers to their neighbour in trying to unseat Assad.
Timber Sycamore eventually became in a diplomatic issue between Berlin and Washington because US weapons to jihadists in Syria were delivered from the US Air Force base in Ramstein, Germany, after they were purchased from Eastern European arms manufacturers under US and Saudi government contracts.
By purchasing “large numbers” of European arms and ammunition and then diverting them to nonstate actors in Syria without notifying the sellers, the US reportedly “violated the terms of sale and export agreed between weapon exporters…and recipients.
“Supplies of materiel into the Syrian conflict from foreign parties—notably the United States and Saudi Arabia—have indirectly allowed IS [ISIS] to obtain substantial quantities of anti-armor ammunition,” the report added.
