It can, but only under limited circumstances, as follows:
1. Terrorist acts can draw the world’s attention to your cause: If the political system in your country simply isn’t responding to your concerns, you can attract attention (and probably sympathy) by blowing up an airplane, or whatever. It’s obviously just a first step, but you have to start somewhere. Would the world be as focused on the plight of the Palestinians as it is without the terror attacks of the 1970’s?
2. You can force people who are on the fence to choose your side through terrorism: This can happen in two ways: either the waverers are intimidated by your brutality; or the government overreacts and turns moderates into enemies.
3. Dramatic acts of terrorism can sap the government’s will: If, for example, Country X is trying to maintain a military presence in far-off Country Y, acts of terror may convince the public in Country X that it just isn’t worth it.
Most acts of terror don’t meet these standards and are consequently doomed to political irrelevance. More on that in subsequent posts.