FBI prevention mandate

TOPOFF 3 and TOPOFF 4, now known as a National Level Exercises, were congressionally mandated counterterrorism exercises for senior law enforcement and first responder officials. TOPOFF 3 took place from April 4-8, 2005, and simulated incidents of biological and chemical agent attacks. TOPOFF 4 took place from October 15-20, 2007, and was designed to prevent or respond to a simulated terrorist attack using WMDs. A National Level Exercise in 2009 focused on prevention of a WMD attack, but not on responding in the event the attack was carried out.

in reference to: http://www.justice.gov/oig/reports/plus/e1004.pdf (view on Google Sidewiki)