I study how a variety of structural and strategic factors affect terrorist mobilization, the likelihood of a splinter faction forming, and the positions adopted by terrorist leaders. The factors considered include the state of the economy, the viability of institutions for the nonviolent expression of grievance, the ability of the factional leaders to provide nonideological benefits, and the risks associated with splintering. The model highlights that, for strategic reasons, changes in the structural environment often entail trade-offs between decreasing terrorist mobilization and increasing extremism. For instance, strengthening the economy or institutions for the nonviolent expression of grievance is found to decrease terrorist mobilization, increase the extremism of terrorist factions, and decrease the likelihood of a splinter faction forming. These results suggest competing micro-level effects of such changes on the expected level of violence that, because they are offsetting, might not be observed in macro-level data analyses, which have been the mainstay of empirical studies of terrorism.