Critics of the program within the Obama administration viewed it as ineffective and expensive, and raised concerns about seizure of weaponry by Islamist groups and about Timber Sycamore-backed rebels fighting alongside the Al-Qaeda-affiliated Al-Nusra Front and its allies.

Initially President Obama rejected the proposal, but later agreed, partially due to lobbying by foreign leaders, including from King Abdullah II of Jordan and Israeli Prime Minister Benjamin Netanyahu.

[12] Timber Sycamore began in late 2012[13][14] or early 2013, and was similar to other Pentagon or CIA-run weapons routing and training programs that were established in previous decades to support foreign rebel forces.

[6][10] Greg Miller and Adam Entous of The Washington Post stated that "The operation has served as the centerpiece of the U.S. strategy to press Syrian President Bashar al-Assad to step aside.

[7] Saudi Arabia, Qatar, and Turkey shipped thousands of rifles, hundreds of machine guns, and large amounts of ammunition to Syrian rebels in 2012 before the program's launch.

[18] The existence of Timber Sycamore was revealed by The New York Times and Al Jazeera in June 2016, after Jane's Defence Weekly reported, in late 2015, that the US Federal Business Opportunities website was soliciting contracts to ship thousands of tons of weapons from Eastern Europe to Taşucu, Turkey and Aqaba, Jordan.

[19] Timber Sycamore was run by the Military Operations Command (MOC) in Amman[2] and provided Kalashnikov assault rifles, mortars, rocket-propelled grenades, TOW anti-tank guided missiles, night vision goggles, pickup trucks, and other weapons to prospective Syrian rebel forces.

[27][12] The magnitude of the theft amounted to millions of dollars, and FBI officials state that some of the stolen weapons were later used to kill two American contractors, two Jordanians and one South African at a police training station in Jordan in the 2015 Amman shooting attack.

[29] An investigation by journalists Phil Sands and Suha Maayeh revealed that rebels supplied with weapons from the Amman MOC sold a portion of them to local arms dealers, often to raise cash to pay additional fighters.

[2] A 2017 study conducted by Conflict Armament Research at the behest of the European Union and Deutsche Gesellschaft für Internationale Zusammenarbeit does not mention Timber Sycamore but found that external support for anti-Assad Syrian rebels "significantly augmented the quantity and quality of weapons available to [ISIL] forces,"[1] including, in the most rapid case diversion they documented,[1] "anti-tank weapons purchased by the United States that ended up in possession of the Islamic State within two months of leaving the factory.

"[9] However, another official stated that ending the program was not a major concession due to Assad's recent victories in the Syrian Civil War, but rather "a signal to Putin that the administration wants to improve ties to Russia.

"[7] Thomas Joscelyn of The Weekly Standard supported the Trump administration's decision to cancel the program, stating "there is no evidence that any truly moderate force is effectively fighting Assad.

"[36] Political scientist Federico Manfredi Firmian called Timber Sycamore “one of the United States’ most ill-conceived and deadly covert-action programs,” noting that it failed to unseat Assad, fueled the war, and inflicted untold misery on the Syrian people.

[38][39] Charles Lister, a senior fellow at the Middle East Institute, criticized the Obama administration for not providing adequate funding and "necessary resources" to FSA units.

[40] In 2016, Canadian right-wing political commentator Rachel Marsden, in a column in The Baltimore Sun, provided her interpretation of the New York Times reporting on Timber Sycamore.