In the ten years since the September 11 terrorist attacks, international terrorist organizations have frequently attempted sequels to the events of that day. No such attempts on American soil have succeeded, a testament to America's law enforcement agencies and intelligence services and to those of its allies.  International terrorism, however, still remains the biggest potential threat to American security.

Though law enforcement and intelligence agencies have prevented any further attacks similar to 9/11 on American soil, the United States has not been free from terrorism.  On the contrary, this country has seen a series of such acts, ranging from bombings to targeted killings to arsons, as well as an even greater number of ultimately unsuccessful conspiracies and plots.  These violent incidents have been carried out not by international terrorists but by adherents of homegrown or domestic extremist movements.  Such movements have historically been the main sources of terrorism in the United States and remain so today.

While the United States must remain vigilant against the threat of international terrorism and devote significant resources to that problem, it must understand, too, that homegrown terrorism will always remain a substantial and consistent threat.  Fortunately, many of the reforms and programs implemented after 9/11 to combat international terror threats have aided in the fight against domestic extremist criminal activity, as well.