The Trump administration has pulled the plug on a CIA covert action program to arm Syrian rebels in their fight against the Assad regime in Syria.

The program, started under the Obama administration, was quickly leaked to the media after its inception, and had continued for four years. The intent was to provide Syrian rebel groups deemed not to be extremists, or ‘moderate rebels,’ with arms, initially in order to combat the regime. The emphasis of the program shifted after the 2015 Russian intervention in Syria to fighting the Islamic State, which was continuing to make considerable gains across Syria and Iraq.

President Obama reportedly had reservations over the efficacy of arming such rebels to exact the original goal of U.S. policy at the beginning of the Syrian Civil War: removing Assad from power. As history has shown, covertly arming groups of foreign fighters has a spotty track record of success, and has at times spectacularly backfired.

But the CIA and eventually the Department of Defense both undertook the mission to train and arm Syrian rebels, with the hope that their presence on the battlefield would stalemate the war, leading to a negotiated ceasefire that would present an opportunity to force Assad out diplomatically. Once the Russians intervened, that optimistic outcome essentially disappeared. The fact that DoD militias and CIA-backed ones were reportedly fighting each other on the ground did not lend great credibility to the effectiveness of the programs either.