The article goes out of its way to not mention it, but it was the Syrian army under Assad who were able to push the terrorists back and recapture the city.
Syria conflict: IS 'withdraws' from ancient Palmyra - BBC News
Islamic State militants have been pushed back from the ancient Syrian site of Palmyra, officials and a monitoring group say. Militants seized part of the town of Tadmur on Saturday, which is located on a strategic east-west route next to Palmyra's World Heritage-listed ruins. Nearly 300 have reportedly died in four days of fighting.
Meanwhile, the number of militants reported killed in a rare US ground raid in Syria on Saturday rose to 32. The Syrian Observatory for Human Rights, a UK-based monitoring group, said that among those killed were "IS oil chief Abu Sayyaf, the deputy IS defence minister, and an IS communications official". US officials had said about 12 militants were killed at the scene of the raid in the eastern province of Deir al-Zour. They said Abu Sayyaf had been killed in a firefight during the special forces raid, and his wife was captured.