NEW YORK — CBS News reporter Clarissa Ward traveled undercover to Syria to interview two Westerners fighting against the United States for stories airing this week, a risk the network took despite the backdrop of kidnappings and beheadings by Islamic state fighters. Ward's stories, about a former Dutch Army fighter and an American who are fighting for rebel groups in Syria, are scheduled to air Tuesday and Wednesday on the "CBS Evening News." [...] this is the first time she has gone since Islamic state rebels, operating in Syria and Iraq, beheaded two American journalists and two British aid workers and distributed gruesome videos of the killings to the world. Among the executives approving her trip was Steve Capus, the "CBS Evening News" executive producer who was president of NBC News when that network's correspondent, Richard Engel, was kidnapped in Syria in 2012.