For the past two weeks we have discussed the opportunities and challenges facing al Qaeda and the Islamic State in the year ahead. As we examined these groups, we largely focused on their core leaders and franchises. But both jihadist organizations seek to inspire grassroots terrorists around the world as well, and though they have recently seen many setbacks, their calls to action will not go unanswered. Grassroots jihadists are homegrown operatives who think globally but act locally. They include people from many different backgrounds who may have close contact with the jihadist movement or next to none. Some grassroots jihadists are merely inspired by like-minded groups they have heard of, such as al Qaeda or the Islamic State, while others have been trained and equipped by professional terrorists.