U.S.-backed rebels in Syria defected en masse to al Qaeda on Sunday, inflicting a major blow to the Obama administration’s strategy against ISIS. Moderate rebels that had been trained by the U.S. either surrendered or defected to the Jabhat al-Nusra group, which is affiliated with al Qaeda. Others fled for the Turkish border. The rebels also lost control of their main northern strongholds in Syria, as well as significant quantities of weapons. The loss crushed the Obama administration’s hope to easily secure supportive Syrian forces in its fight against ISIS.