Terrorism... What's the point?

I saw an ad on the discovery channel for a show documenting 9/11 and it got me thinking.  What is the point of terrorists doing the things they do?  I mean did they really think our government would just roll over and do nothing?  Instead we go off to war, which pisses them off and results in more terrorist action (carbombings, suicide bombings), which results in more military action, which leads to more terrorism...  The whole situation is a fucked up lose/lose scenario.  What do these fucking insane idiots hope to accomplish!?

Terrorism is basically a propaganda term and essentially has no meaning.