BEIRUT — A number of U.S. service members were killed in an explosion while conducting a routine patrol in Syria on Wednesday, the U.S. military said, an attack that came less than a month after U.S. President Donald Trump announced his intention to withdraw troops from the war torn country. The Islamic State group claimed responsibility for the rare morning attack, which local groups said killed 16 people in the U.S.-patrolled town of Manbij. The claim, which could not be independently confirmed, calls into question Trump’s claim that IS has been defeated in Syria — his stated reason for pulling 2,000 American troops out of the country. “We have defeated ISIS in Syria, my only reason for being there during the Trump Presidency,” Trump tweeted in December in announcing his intention to bring back U.S.