The terrorist attacks of 11 September 2001 (9/11) exposed a disturbing weakness in the security of the American homeland. For more than 200 years, the United States had prepared itself to defend against foreign invasion, nuclear attack and other external threats. Minimal thought was given to the ability of non-state actors to infiltrate highly-trained sleeper cells into the American homeland and with little or no warning inflict massive casualties and damage through a catastrophic terrorist attack. Earlier incidents, such as the 1994 World Trade Center bombing, were treated as little more than nuisances and considered the domain of the FBI and local law enforcement. However, in the years after 9/11, the U.S. government has undertaken many significant changes to ensure that similar attacks would not occur. In May 2009, the White House announced the absorption of the Homeland Security Council (HSC) into the National Security Council (NSC) as part of a larger reorganization of the presidential national security policymaking apparatus, thereby including homeland security in a more expansive and integrated definition of U.S. national security.