While it’s no secret that the CIA has had a “covert” program supplying weapons to Syrian rebels for years, and it’s likewise no secret that Saudi Arabia has been throwing large sums of money and arms at rebel factions, it’s only now being understood how closely linked those two schemes were.
The administration is said to have seen the plan as a way to get control over the Saudi arms smuggling into Syria, fearing the Saudis would be willing to send arms to factions the US wouldn’t see as allies. This largely didn’t work, of course, meaning the US-Saudi arms ended up more or less everywhere.
The Saudis, meanwhile, saw letting the US in on their arms scheme as both a rubber stamp for continuing the program, and as a way to oblige the US to let them be involved in the final settlement talks on the Syrian War, and back Sunni Islamist factions.
The TOW anti-tank missiles and Chinese anti-aircraft missiles that ended up in the control of various rebel factions, including ISIS and other Islamists, were provided by and large through the CIA program, and sourced and paid for by the Saudis.