From The president's speech this morning:
...
Over the years these extremists have used a litany of excuses for violence -- the Israeli presence on the West Bank, or the U.S. military presence in Saudi Arabia, or the defeat of the Taliban, or the Crusades of a thousand years ago. In fact, we're not facing a set of grievances that can be soothed and addressed. We're facing a radical ideology with inalterable objectives: to enslave whole nations and intimidate the world. No act of ours invited the rage of the killers -- and no concession, bribe, or act of appeasement would change or limit their plans for murder.
On the contrary: They target nations whose behavior they believe they can change through violence. Against such an enemy, there is only one effective response: We will never back down, never give in, and never accept anything less than complete victory.
...
If anybody wants to read the
full text, click here. This is by far the best explanation of the War on Terror that I've ever heard from the White House. It's a really long speech, but reading it all is well worth it.