Thanks to a "lurker" for the pointer to this open access article in a journal I rarely see, 'International Organisation' by Virginia Page Fortna:http://journals.cambridge.org/action...000089#cjotab_

The Abstract states:
How effective is terrorism? This question has generated lively scholarly debate and is of obvious importance to policy-makers. However, most existing studies of terrorism are not well equipped to answer this question because they lack an appropriate comparison. This article compares the outcomes of civil wars to assess whether rebel groups that use terrorism fare better than those who eschew this tactic. I evaluate the advantages and disadvantages of terrorism relative to other tactics used in civil war. Because terrorism is not a tactic employed at random, I first briefly explore empirically which groups use terrorism. Controlling for factors that may affect both the use of terrorism and war outcomes, I find that although civil wars involving terrorism last longer than other wars, terrorist rebel groups are generally less likely to achieve their larger political objectives than are nonterrorist groups. Terrorism may be less ineffective against democracies, but even in this context, terrorists do not win