Fear & Inaction

What is it that could make people mad enough to act? What is it that could motivate them into action? I mean, there are regimes out there that have persecuted, starved, and humiliated their peoples using all hideous tactics conceivable to the human mind, and yet, their victims remained inactive, inactive on account of their fear, of their sense of and desire for self-preservation. What does that mean? Is the threat of genocide the only way to get people to break through the barrier of fear?