Emergency management and Terrorism

Terrorism is a 21st century fact of life in the United States of America. Unfortunately, no community is immune from the threat.
But what role, if any, does emergency management (in any community, small or large) have related to terrorism incidents?

1. What do you believe is the role of emergency management before an "eminent" terrorism threat… if, for example, you are made aware by law enforcement that an attack is forthcoming?
2. What do you believe is the role of emergency management during a terrorism response?
3. What do you believe is emergency management's role following a terrorism event?