  In fact, the comparative weakness of some who use terror means that they frequently need to engage in repeated acts of violence in order to establish their credibility with respect to any subsequent demands and threats they might make. It is unlikely that a group will be able to gain acquiescence to its demands by threatening to use terror tactics if it has not already engaged in such activity. But while the use of terror often betrays a relative weakness, those who use it also often rely on stealth, geographic dispersion, and choices of soft targets, making their attacks both very difficult to prevent (at least in ways that are consistent with significant openness in one's own society), as well as very difficult to retaliate against.