Leaders of the al-Qaida and Islamic State terrorist groups have been urging followers in Western nations to carry out attacks with whatever weapon is available -- including a knife, a car or a fist. This month, Mohammed Bouhlel showed how deadly simple attack methods can be. He killed 84 people in the French port city of Nice with a truck. Daniel Benjamin was a counterterrorism official at the U.S. State Department. He is now the director of the John Sloan Dickey Center for International Understanding at Dartmouth College. “It’s a frightening moment,” he said. “How many easy and simple ways can we identify to kill people?” Terrorists have begun using vehicles as weapons for several years. So-called car-ramming assaults by Palestinian militants have killed many people in Israel. Vehicles have also been used in a series of smaller attacks in France, Britain, Canada and the United States. In 2006, Iranian-American Mohammed Reza Taheri-azar drove his car into a group of students at the University of North Carolina.