You might recall that the 9/11 and 7/7 "terrorist attacks" happened during exercises such as  this FEMA drill.

Even if this exercise remains just an exercise, I expect the PEOPLE to be TERRORIZED.  As a nice side benefit, the population becomes used to the military including troops from OTHER countries in AMERICA.  I'm sure glad I live in Arizona.

The details are at the FEMA site:

National Level Exercise 2009 (NLE 09)

Enjoy the terror!